I've been using this lense for about 4 months now & can't hardly stop using it. This lense has produced some of the best wildlife/nature shots I have ever taken. It's almost became my primary/walk-around lense now, even for indoor/portrait style shooting. It's not very heavy & the IS on this thing allows you to take amazing handheld shots, even on fast moving subjects such as birds or athletes.
To be honest, I really don't know what all of the fuss is about this: "images start to crap out after the 200mm mark". Unless you're just one of these people who are very anal about everything and apparently, look at finished pictures under magnifying glasses or something, I've gotten superb results within the entire range of this lense. I'm constantly shooting subjects 'wide-open' (sometimes even with a tele-converter), & still resulted with excellent, crisp, sharp images. (But then again, I'm still one of those guys who believes that 'lesser images' is usually the result of the photographer, not so much the camera or lense.)
The only 'con' that I found with this lense is that it's not compatible with the Canon tele-converters. I've heard that Canon might be releasing some newer tele-converters that will be compatible with the 70-300 IS/USM, but as of now, no. I was forced to buy a cheap ($80)Quantary 2X converter instead. It still has allowed me to get a bit more reach if needed as well as some darn good pictures, but you lose your IS feature & the AF is pretty limited.
Other than that, I think this is one hell of a good lense for the price & would highly recommend it to anyone over the 70-200 w/o the IS if you're going to be doing a lot of handheld shooting. The IS feature alone has 'saved' more pictures for me than I could tell you. Great lense.