Let me start by saying I don't know anything about Kundalini yoga other than what's in this video, so I can't speak to whether it's authentic, dumbed down, etc. But I think this tape is a pretty good workout for someone like me, i.e., no back or knee problems, 5 months after having her third kid wants to lose those last 10 lbs. and get back into some semblance of shape, needs a relatively short workout and generally likes the stress-relieving aspects of yoga.
This workout is actually tougher than it looks -- although it can be done by "beginners," many (including me) will initially find it impossible to get completely through without some rest or modification. Even though I like to think I have pretty strong arms (carrying around a big baby), I was shocked at how tired my arms got from simple activities like raising them and lowering them, making punching motions, shaking them, etc. Most of the movements are simple, but after you do them a few minutes, you realize that isn't so easy.
As far as Gurmukh is concerned, my reservation is that if you are the type of person who is easily distracted by this sort of thing, Gurmukh's manner may be irritating. She reminds me of that one flaky high school teacher we all had who seemed to be in her own weird world -- half the stuff she says sounds like she is making it up on the spot, and it doesn't make a lot of sense (to me, anyhow). Depending on what mood I'm in, stuff like "A flexible spine is a flexible mind . . . and a flexible mind is a flexible life . . . " or "Stretch your arms out like the biggest wings . . . the biggest wings you ever saw . . . or ever felt . . . " can really get on my nerves day after day. On the other hand, when you're going on your second or third solid minute of fluttering your arms up and down and you think you can't hold them up any longer, her exhortions to use the motion to release of all your stress and anger can give you a second wind. Plus, I think she is in her late 50's or early 60's and she looks amazing, and moves with unbelievable grace, strength and flexibility (which is why this video is deceptively tough -- she makes it look easy). If this is how to get that kind of grace, strength and flexibility at any age, sign me up! But I can see why a lot of people are weirded out by Gurmukh and the stuff she says. If you are sensitive to that sort of thing, you may find this tape irritating.
But overall, I think it is a good tape. It's less than an hour, includes warming up and relaxing activities, but the middle portions will really get your heart rate up. I think it is a good choice for people who maybe want something a little more active than "regular" yoga, and like the spiritual aspects of yoga, and don't want to go for a full-on aerobics tape. You will definitely feel it in your arms and legs the day after you do this tape!