Just a related note:
I have had an iCurve for close to a year now, about 3 months ago, my PowerBook started sliding off it. It never occured to me that heat could cause the problem because iCurves are designed to handle that, but I do type on it quite a bit (despite having a full-size keyboard plugged in) so I thought that maybe I'd bent the iCurve down so that the angle was too steep.
I e-mailed Griffin about it and they explained that the problem was caused by dust build-up on the pads. I followed their cleaning instructions and it's good as new now.
If you leave the laptop on the iCurve most of the time you may never have a problem with it. I take mine with me a lot otherwise it probably wouldn't have slipped