I love this pack and I will tell you why but if you read anything... read the end of my review about the warranty.
I began using this pack when my kid was 21 lb's and 7 months and he is now 1 year and about 25 lb's. He rides safe, secure and comfortable in this pack. When I first began using the pack he would fidget or whine a tiny bit when strapping him in but once in he is quiet and happy. Once I used the pack for a couple of weeks he was thrilled to be put in it. I have carried him around for three hours in a theme park and he was content and excited to see all of the action from a grown-ups point of view. He has fallen asleep in it with his head forward and face turned to the side resting on the very soft and plush dribble pad (removable and machine washable). Security and comfort are certainly not an issue with this backpack. There are circulation worries with some packs because of dangling feet. On the FC 3.0, the childs feet have a resting area. For larger children you can use the optional Kelty stirrup accessory when your childs is tall enough that their feet have to go to the outside of their seating area. The stirrups are an older item but the rings they clip onto are present on this pack. You shouldn't need these until your child is closer to two or older.
Next... I am very comfortable wearing the pack. I am 5'11" and about 180lbs. When I first tried out the pack with the factory settings it felt good. I put my kid in it and tightened some straps up and it was fine although the shoulder and chest area seemed to be carrying the lion share of the load. Then I raised the torso belt some and it was better. I went to a theme park for a day and pulled the shoulder straps even tighter and it raised the pack a little higher on my back. At this point the torso buckle was just about at my belly button and the pack just sort of hugged my back and the weight distributed nicely and I knew I found the sweet spot. This was our first major outing. We logged three hours on a sunny 70 degree day.
On the subject of sun; The sun/rain hood is well designed. The child will have a great view off to both sides. I have heard some grumbles from fans of other brands about the Kelty hoods because they obstruct the front view a little. What these people do not realize is that the child does not need to see straight ahead very well because Mom and Dads head is in the way anyhow. They will have a good view of the back of your head so they are comfortable knowing it's you carrying them and they will have a great view on the sides to see everything else.
The generous storage areas consist of four compartments. One compartment stores the sun/rain hood which is included. One compartment holds an included padded changing pad and has room for a jacket or extra clothes etc.. The third compartment is a small compartment and the last is a very big one at the bottom. I can fit a small picnic blanket in there. You can actually leave the diaper bag at home. I fit diapers, wipes, toys, bottles, extra clothes... I really do not bring a diaper bag with me when I use this pack.
Putting on the pack is generally safe and fairly easy after you practice a few times, take your time and use caution. The FC 3.0 pack is tall so the shoulder straps are higher off the ground. I have very little trouble strapping on the pack from the floor. I can just loosen the shoulder straps, squat down and put the shoulder straps on. Then I lean forward to get him off the ground and shift his weight onto my back (rather than have him flop over to a side) and then stand and buckle the torso and buckle the chest and tighten the shoulder straps. I am a little overprotective yet I feel very confident and safe loading this pack onto my back with my little guy in it. Unloading involves loosening the shoulder straps, squatting down and resting the kickstand on the ground. With that said... Loading and unloading from a raised area such as a bed or the back of an SUV is far easier. Also, you will find park benches make is easy to load and unload.
This pack is perfectly designed for neighborhood walks, a day at the park or zoo and even serious hiking and overnight camping. I originally thought it was overkill for grocery shopping or a mall but after using this pack for several months now I take it and use it everywhere. My kid makes it about 10 minutes in the grocery store/Target shopping cart. He is good for 30 minutes or more in the pack.
Finally; I need to tell you about my warranty experience with Kelty. One of the best reasons to buy a Kelty product is their Lifetime Warranty. I had an older Kelty child-carrier backpack in which a strap and buckle wore out (this was a less important strap not jeopardizing child safety and the new models have a reinforced version of this strap and buckle). Kelty has a lifetime warranty and they advised me that they do not usually repair the child carriers but will replace them. I was instructed to cut the straps off of my pack (making it unusable), the tag from the pack showing the model number and mail them to the company along with a simple form I filled out from their website. One week after mailing the straps I received a brand new FC 3.0 from UPS. The model they replaced was an older and somewhat less expensive model. I was shocked at how fast they shipped it out to me and that they sent me their top of the line carrier. I paid about $5.00 to ship the straps back and they paid the shipping on my replacement pack. Wow. There are a lot of choices out there for child carriers but I have not seen a lifetime warranty on any brand but Kelty.
This warranty experience has made me a big fan of Kelty as a company. My experiences with this pack has cemented that loyalty. This child carrier provides a generous amount of storage, a comfortable carry for Mom and Dad and most importantly a comfortable and safe ride for your child. If this is what you are looking for than you have found your carrier.
Update Feb 1, 2011. My son is now 18 months and and 26 lb's and still likes being in the pack. I put him in it for hiking and walks. It is still a good choice for theme parks because of all the storage it has. He likes to run around a lot more these days but never gripes when I put him in the pack!