I've been using this site since the xoom released to try to keep up with the newest xoom optimized apps and i keep seeing people saying they only want the wifi only version.
I just don't get it.
Considering the convenience lost it's a small extra price to have the 3g/wifi model. Even if you intend to only use it at places with wifi, you lose the option of one day adding 3g and even 4g if your needs change. I need 3g because I am usually away from wifi access, but even if i spent most of my day in my office I would have the 3g version so I wouldn't be tied to a router.
Why not get the 3g/wifi version and forgo the data plan until you need it? Then you could just buy a month of data whenever you go on vacation, or take a business trip, etc..
My friends with iphones don't get 3g here because AT&T sucks in my area, and they are always hunting for wifi availability so they can surf with some speed, the last thing I would want to do with a "mobile" tablet.