Well I just upgraded to 3GS last week and since I had their Xylo case for my first iPhone, i ordered their new Quattro case for my 3GS.
Got it on Saturday and been using it for couple of days now, this thing is just amazing.
It offer an all around protection like the Xylo case that I had but the problem with that case was it got scratches after a year or so since it was a clear case, this case has a soft silky finish to it. It's still a hard case though, it also covers all the ports and opening with a soft silicon memebrane. All ports are covered inpeccably.
The best part of this case which still set ivyskin apart from all other makers is the glass touch screen. It works, it's like having an iPhone screen over the iPhone screen
While being a bit costly at $45, I can assure you it is made to a much higher quality than any other case I have seen or used. The hard shell has a much stiffer feel and is covered with a cool coating that doesnt attract lint and dust in your pocket. Overall much better than any other iPhone case.