I have one, for my 15 inch powerbook. I find it to be very light and comfortable, and I like the way it looks--it matches the powerbook perfectly. The craftsmanship is very nice as well. I have no complaints. I use it when sitting on a couch primarily -- so my powerbook can breath and I don't have to worry about the heat, although you can take the padding off the front end and use it on a desk.
I have one for my 17" Power Book - absolutely love it! I use it everywhere, home - work - desk - comfy sofa- and it works like a champ to keep my computer cool. Seemed a bit pricy when I was shopping around for a stand but now that I have one I've found that it's absolutely worth it.
I usually leave the front rest attached even on my desk as I usually use an external apple keyboard in that setting. I was concerned about using the optical drive when the front rest is attached but it turns out it's not a problem. i just lift the front of the book when it's time to insert or eject. It's a lot more convenient than it sounds