Like any other convenience, 3G is nice to have. Sitting at the end of a runway staring at a sky that was not forecast that way is a great time to be able to pull out your Ipad and look at some real time weather, rather than taxi back in and hook up to some wifi. That scenario can make 3G very worth it and I have been in that situation, without 3G, so I wished I had it even more then! If you want to be as frugal as possible though, you can do just fine without it as well.
I am hearing a lot of rave reviews from the Ipad in the program.