I just received my CP-321 official Nokia case for the N900 from handtec.

Fits snugly over the phone - the cut-out at the top leaves the Nokia logo exposed.

However, as you may expect, it's a bit of a nightmare to get off when you receive a call - I have found the best way is to squeeze the bottom and ease the phone out of the top.

Also, if you have a handstrap attached, when putting the phone back into the pouch you have to dangle the handstrap through the hole in the bottom of the pouch before pushing the phone in.

So, I will only be using the ouch when the phone is in my pocket - when I get to work etc. it'll stay out of the pouch on my desk.