Tablet PC, too many choices, ARRRGH!!!!!!!!!!

hey everyone
I need some advice
I am going to be investing in a new tablet pc in the next few weeks and im tearing my hair out trying to decide which to choose.

Heres what i need from it:
- light weight (sub 4lbs) – most important
- windows vista capable (i am more than happy to do things like ram upgrades if necessary)
- passive and digitilizer screen preferred
- long battery life (6+ hours)

I dont need things like big hard drives (60-80g is more than enough), i dont need a super powerful machine, or a dvd drive, but it must have wireless.

Consider cost to not be an option, i just want opinions on different systems

thanks
PS: at the moment, im looking at a lenovo x61 tablet, so any opinions/comments on that would also be appreciated