I recently purchased an iLap for my PowerBook. It provides excellent heat distribution, raises the screen and tilts the keyboard when it is on my desk, and when it is in my lap it raises the PowerBook to a much more comfortable position and keeps the heat away from my future children.
The most important thing is that it really relieves some of the strain I constantly feel down the back of my left shoulder and neck after prolonged periods of notebook use at a desk. I think it looks really good on my desk and now I can slide the notebook around the desk rather easily (I have a glass top).
It is incredibly comfortable for lap use as well — you feel absolutely no heat from the PowerBook and it raises the notebook to a level that is much more conducive to extended sittings. The machine stays much cooler; it's almost cold in places where it was rather warm before.
I was a little concerned about the angle of the slope being large enough to prevent a CD/DVD from being loaded into the PowerBook (it slot-loads from the front), but this was not a problem at all.
Aesthetically, there is one thing that irks me: the padding found on the front of it has this ugly (in my humble opinion) "shell" pattern that I really can't stand. I knew this before I bought it so I can't complain too much, but if I had my say this pad would be as plain as possible. Moreover, it's made out of velvet; I would have preferred anything else.
Functionally, I don't have too much to complain about, but there is one thing that kind of bothers me: there is no way to lock the back hinge in place. This is fine when you have it on your lap because it allows the iLap to move along with the position of your legs, but when you slide the unit around on a desk the hinge moves a little and I find myself checking to make sure that it's straight. I would have liked some sort of locking mechanism on the hinge.
There were a few things that surprised me about the setup. The first is that the front pad attaches to the unit by velcro. It obviously had to attach someway, but velcro never crossed my mind. The downside to this is that attaching/detaching the front pad is a pain, especially if you are frequently moving between a desk and a chair/couch. The upside to the velcro is that it makes it easier to slide the whole thing when it is on a desk (instead of having the aluminum touch the desk).
Another thing that I didn't anticipate was how the screen's angle would be constrained by the angle of the iLap. Those of you that have a new aluminum PowerBook know that the screen does not tilt too far past 90°, at least compared to the titanium PowerBook, or most notebooks for that matter. The angle of the iLap works to cancel out the angle of the screen so as to further suppress its maximum obtuse angle. In practice this really isn't a big deal, especially if you sit properly, and I really don't see how they could have designed around it, but I'm sure this will be an issue for some people.
Finally, the screen tends to "bounce" quite a bit when you are typing fast. This is no doubt due to the fact that the back hinge is wrapped in a cushion which tends to react to the weight and movement of your fingers as you type. I suspect that this "bounce" will dissipate over time as the cushion becomes compressed from use.