I have one 18-55mm lens and a cheap 75-300mm. I don't see myself carrying a tripod around, so what I could use is something with an image stabilizer. Canon also has the 28-135mm with IS and that's probably what I'll end up getting. It's not an 'L' lens like the 100-400, so it's fairly affordable.

-tek

(I still make that other stuff too with those things whatever they're called there in the corner.)