I'm getting the 3G version. The whole idea behind a Tablet for me is mobility, instant access to the web, basically a bigger, more capable version of Droid. While I have a rooted phone with wifi tether ability, pulling out the phone, starting wifi tether, waiting for the tablet to connect completely defeats the notion of immediate access while on the go. I may as well stick with tethering my netbook to my phone.
Now granted, it costs $200 for the hardward plus the monthly fee, but having that capability is worth the $20 a month for me. If I know I'm going to use serious data, maybe I'll look for a Starbucks or break out the tether, but having the data package is what will make a tablet a truly useful device in my opinion.