I think it looks like it is probably a great lens, just like the non-IS version. I can see times when IS could come in REALLY handy. The lens doesn't look much bigger than the original at all. It would definately work to carry around all day.
As for the 2.8 vs. IS, it really comes down to different strokes for different folks. I think the 2.8 and the f4 IS should be right around the same price so that you can choose whichever one fits your needs better, without having to figure the cost in as much. For people who shoot a lot of moving subjects, f2.8... For people that shoot more stationary/panning subjects, f4 IS.
----Brad----
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