I have the non-IS 70-200 as well, it's great. IS is one of those things that's nice to have, but isn't really necessary.
I do like having it on the 300 f/4 that I'm borrowing right now though, not having that extra stop (2.8) makes a pretty big difference at that length......
That's another reason I don't like the teleconverters, your 2.8 turns into an f/4, or a f/5.6 with the 2x...... autofocus performance goes to shit, and if it's dark you're screwed.