It's alright. I used it quite a lot over the past couple of weeks on a trip to India. At iso 100 it shoots nice, clean landscapes with a perfectly good dynamic range, although I would have benefitted from a tripod and ND filters. The street stuff I was doing at night was a bit more challenging for it at iso 3200 but it does clean up ok. However, at these higher iso's the DR and colour starts to be affected as well. The shots are not unusuable at all and a fiddle in lightroom does them good.
Its overall higher iso performance is now lagging behind more modern sensors but the pics do clean up well enough. From iso 800+ you do start to notice noise, espsically in green shadows (look at a lot of bird shots on green backgrounds and you will see it) but this is eaily dealt with in LR. People get their knickers in a twist about the 7D's performance (either accusing it of being terrible beyond 800iso or claiming they can shoot cleanly at iso 3200) but the fact is that it is now ~3 years old and the sensor is showing its age in comparison to the newer ones. However, it is still producing great shots and is usable up to 6400 as long as you can clean up in LR and are happy with some noice in the photo!
Sorry for rambling!