The phone does look great with nothing but, nobody is perfect. Without protection your phone WILL show signs of wear. At the very least I would use a screen protector. A good one is barely noticeable. As for cases, thats a tough one. I used the krusell for a while but only out of necessity...it looked like crap. I found this on ebay the other day and I should be receiving it soon.

Hard Rubber Case for Sony Ericsson K790a + Belt + Strap - (eBay item 150191014189 end time Dec-09-07 22:07:49 PST)

Looks decent and should protect well against drops...I think.
I'll let everyone know after I road test it a bit.
Woo-Hoo! first post! ;)