This lens was EISA best consumer lens 2008-9, a redesign of the long standing full frame non stabilised lens. Sigma and Tamron have done a great job with their wide range superzooom lenses. This is one of the best. I hve tried it on a Canon 40D and a 5D Mark 2 and it gives exceedingly good images on both. It is a little slow and soft at the 300mm end, but still very good. A light weight of 500G is excellent for a large IS zooom lens, and it is pleasantly small when not extended. It will take acceptable macros, I recommend looking at the groups for this lens on Flickr. Well, I was impressed!
For a walk around lens with such versatility it is a reasonable price and excellent quality. Suitable for the enthusiastic amateur for most purposes, but it is a jack of all trades, so shorter zooms or primes will be better, but at what price? The image stabilisation works very well, up to 4 stops improvement.