I do tethering!
My new iPad is wifi only but my Galaxy Tab has a 3G month to month plan with Tmobile: 30 dollars (with taxes) and unlimited data plan. I found the GT being a perfect travel companion for my Kindle 3 wifi or even iPad.
I did not choose the iPad 3G because the available AT&T options are too expensive and restrictive, in my opinion. Also, I bought it with my couch and house's Internet on my mind, not planning to take it out for long trips. If that happens, tethering is my Plan B.