I'm a certified personal trainer, I've been lifting regularly for nearly a decade and after 3 months with my Selectech 1090 dumbbells I can tell you with absolute certainty they are the best purchase I've ever made to get a stronger, more muscular body.
First off let me tell you why I decided to get them since my motivations will help explain their benefits:
Already knowledgeable on lifting - Like I said, I'm a certified personal trainer and I already know how to do tons of exercises with proper form. If I had no idea how to do strength training, these dumbbells would be pretty intimidating, and I'd probably want to get a home gym machine to guide me through the proper motions.
180 is Just Right - For someone light the 1050's that are 50 pounds would probably be adequate resistance. By the same token, if your a 250 pound lineman on your Division 1 College football team, or a power lifter these weights will be inadequate for you. 180 pounds is enough resistance for most people, but if your an elite athlete in a high weight class these just aren't going to cut it long term. You should go with a full olympic weight set.
I weigh about 180 pounds, so I figure If I can bench, row, squat and deadlift the dumbbells which are equivalent to my body weight for 10 reps I'm strong enough and don't need to worry about getting bigger. I think most people feel that way and these will fit the needs of the vast majority of users.
Workout By Myself - If you have a spotter to help you adjust weights, or spot you from dropping a heavy bar on your throat then barbell sets are a little more appealing but since I work out by myself, quickly adjusted weights and dumbells that I can let go of without decapitating myself are very appealing.
Limited Space - I didn't want to fill a room with a whole gym or weight set. These take up virtually no space in the corner of a room.
Good Investment - Buying all the dumbbells you'd need to have 0-90 would cost well over a thousand dollars, these are an incredible deal given the flexibility they give you.
Glutton for punishment - I love doing drop sets where after I reach muscular failure with a weight, I quickly reduce the weight squeeze out a few more reps and continue on like that until I pass out, throw up or get stronger. Changing weights with the turn of a dial could not be faster or more convenient. I like to keep my workouts pretty intense and short, not having to waste time or focus fiddling with dropping and adding weight helps me get a better intense workout more quickly.
Too Lazy and Cheap for Gyms - I'm one of those freak shows that actually really enjoy working out, but I'm way too lazy too commute to the gym, and too cheap to pay for membership. Plus I get hot and I'd rather workout with my shirt off which would be weird at a public gym. I have an easier time making sure I get my workouts in when I can just pick up and do it whenever I feel like it without going out of my way. I'd been doing body weight exercises like pushups and squats for a while and I was happy with it, but I wanted to throw something new at my body and increase the intensity of my workouts. These give me all the convenience and flexibility of a home gym, without having to give up an unreasonable amount of space or money.
Dumbbells Rule! - Dumbbells are better than machines or barbells for real world strength. Not only do they develop your stabilizing muscles and core better, but they get both sides of your body strength symmetrical, unlike machines or barbells where the stronger side can pick up the slack from the weaker side. If someone can bench 100 they won't be able to dumbbell press that much, where as someone who can dumbbell press 100 will be able to bench much more!
Love Bodyweight Exercises: I believe the body responds better to bodyweight exercises like dips, chinups and squats than equivalent exercises that don't move the body through space like machine leg presses or lat pull downs. So I'd actually rather use dip/chinup tower with added resistance from the dumbbells on a dipping belt rather than, use equivalent exercises on a machine.
More on this, and a full description of the product features:
Highly Recommended with a Dip/Chinup Tower and Lifting Belt!
Professionally, I sell breakdancing competition and instructional videos like this:International Battle of the Year 2008 and Storm's Footwork Fundamentals, I've been break dancing for years and triceps are the most frequently used muscles for handstands, and power moves like flares and headspins. Dips are my favorite tricep developer, and I've been doing them for years, long enough that I was ready for some added resistance beyond my own body weight.
I'd tried filling a camping backpack with dumbbells, but it was very uncomfortable (The steel weights dug into my back), it was difficult to put on, it made me back heavy so I felt like I'd fall backwards and be like a turtle on it's shell unable to get up, and it would be incredibly time consuming to adjust the weight, I'd have to take off the backpack and slowly add or remove weight, zip it up and put it back on, it would take several minutes, and be a disruptive hassle. I have a dip and chinup tower and when I got the 1090's I started out doing dips and chinups holding the handle between my feet. That worked okay, but it's hard to concentrate on holding it with your legs during the lift, and because the dumbells are so long, if your dip/chinup tower isn't extremely high, if you go the whole way down holding the weight between your feet you'll smash your dumbbell on the ground.
So I invested in this 20 dollar dipping belt from amazon Altus Athletic Nylon Dip Belt It works great and is extremely comfortable, the only thing I didn't like is the chain just seals around the dumbbell handle with a hook, and I wanted something more secure, so I got a 2 dollar little speed carabiner from home depot that securely fastens the dipping belt chain shut around the dumbbell handle and holds it securely. So I'd recommend if you want to do dips and chin-ups you get a dipping belt and carabinier, they are cheap, and change it from being a chore to being a pleasure. With the help of my dipping belt and the 1090's, in the past 3 months I've worked up to doing 12 dips with 60 pounds, and 5 chinups with 60 pounds. My friends jaws drop when they see me banging out reps while hauling the extra weight. I plan on working up to performing chin ups and dips with the added weight of the full 90 pound dumbbell.
The Dials: It's incredibly fast and easy to select your weight. The dials are sturdy, clearly labeled, fast, accurate, and allow for different settings on each side of a single barbell, so if you want to curl 32.5 pounds, you just set one side at 30, the other at 35 and your good to go. Very occasionally (maybe 1 out of 100 times) if I don't put the dumbbells back down into their holder properly the dial will lock up slightly. But if I reseat the dumbbells properly, or knock the dial down to 0 and put the handle pack in it's place it's back and good as new. Note that if you always put the handle in perfectly this won't happen, but you will probably occasionally set the handle back down into the dumbbells at an off angle, whether you have the stand or not.
The Dumbbell Stand: Get it. I didn't think I'd need it, but these bad boys are really heavy and tough to move around without the stand. The stand is pretty easy to put together, looks cool, it's space efficient, sturdy secure, and super easy to move around on it's wheeled base, so you can bring the weights out of the way, or over to your bench, and save the energy you would have used wrestling them up from the ground to instead set a new personal best on your lifts! The stand makes these much more convenient and more of a pleasure to use.
The Bar (Gloves not included):
I have medium to large hands and for me the round-rectangular shape of the handles are perfectly comfortable, I don't mind them not being round. With that being said the metal on the handles is VERY textured to give a better grip. For light lifts of 10-40 pounds this feels okay on bare skin, but when you start doing lifts with the full 90 pounds and you have soft hands these will RIP you up. This doesn't bother me any, I always lift with workout gloves and with those they couldn't be more comfortable. If your hands are crazy tough or you don't usually lift heavy don't sweat it, but if you lift heavy and you like having skin on your palms, you need gloves for these handles.
The Dumbbell Size: The dumbbells are a little long compared to standard ones. I never find them difficult to use or troublesome, but they are a good 6 inches longer then standard dumbbells just so you know.
Okay, that's about as thorough a review as I can give. Sorry it's long but I figured you'd want to get all the details before you shell out $500+ They're well made and as long as you don't abuse them and throw them around the room they should last you for decades of regular use. I could not possibly be happier with these or recommend them more highly. If the benefits that appealed to me, appeal to you pick these up. You'll be glad you did.