I have this lens, Its an awsome zoom lens, Image quality is very good with excellent contrast and little or no colour fringing at all and about as good if not better sharpness as a 70-200 f2.8L. It weighs about 1kg is made of metal contruction is comfortable to hold and focus ring is on the inside with the zoom at the end of the barrel, some dont like it but i prefer it tbh, It has a 4 stop immage stabalizer and focusing is internal with full override. But all in all I would say its a superb all round zoom lens but because of the apeture not much good inside without good lighting or high iso. Only downside is it comes with no tripod mount ring and a canon one costs around £140 but you can get a good cheep alternative for around £30.
I would head over to Dxo Mark or pixel peeper if you need to compare performance. At £905 its a bargain imo.
A cheaper alternative is the tamron SP 70-300 DI f4-5.6 at around £340 but the quality is nowhere as good.