But it always good to scan just to be on the safe side. With the new mobile viruses that are coming out, first hit the iPhone and on wmpoweruser.com they had mentioned a virus that causing charges to your phone by-way of premium text messages. In any case, I'm using ESET Anti-virus Mobile for PDA's:
http://www.eset.com/products/mobileantivirus.php
Check it out, its pretty good, I've been using it for a while!