I have this, and it's changed my working habits SO much for the better. First, it keeps my hot little MacBook Pro off my lap - and this thing does get really hot.

But I actually use it mostly at my desk, where the perfect angle has dramatically improved my posture (as a mom, I already have enough ways to get an aching back, thank you very much, so decent posture at work is pretty crucial).

I really love this thing - saw it amidst a million other things at MacWorld. It's the only one I bought, and I would highly recommend it to you!