The Silicone case cost me 220/- from Binary Systems in Trivandrum.
It feels pretty OK to the touch, and is non-slippery. You can leave it on the dashboard of a running car, and it will not run all over the place. However it tends to pick up dirt fast - and I mean Fast.
Its easy to put on and remove, but it makes the phone look bulky. The sleek futuristic look is lost. Also there is absolutely no protection for the screen. But then I guess the Gorilla Glass doesn't need any in the first place.
Also protects the phone from minor drops and impacts. I have already dropped my phone once from my desk by accident, and the phone did not even suffer a dent in the plastic.
Oh, and one more thing. You can almost guarantee that the phone will not slip from your shirt pocket, even if you bend almost double.
So all in all a good buy, if you do not mind the drop in cosmetic appeal.