I got this as a replacement for my seemingly dying Zyxel p-662h-d1 that started dropping sync every few minutes or so. If you've configured Cisco h/w before, configuring this is a doddle, and it syncs up _faster_ than the Zyxel.
If you need a Cisco router for a small office on an BT 21CN ADSL2+ line I suggest you avoid previous Cisco ISR versions and go for the VA model. For whatever reason it has taken a few attempts to get stable hardware/firmware for these lines - see http://stewartandrews.wordpress.com/2012/06/28/cisco-cpe-and-compatibility-with-bt-adsl-services/ for a useful summary.
As usual with Cisco stuff it's very powerful and flexible but configuration can be challenging. You probably will also want to buy a Cisco SMARTnet contract to get IOS updates and support. Once correctly configured though it is very stable.
After two days of an experienced IT engineer trying to set it up, we gave up and sent it back. We had to pay a "re-stocking fee" which was annoying, The router came without even the web app required to set it up and that had to be loaded by command line in a terminal interface. No doubt it was possible to get it working, but we didn't manage it. Unless you really know how to implement one of these, I would advise against it! The PC software requires an old version of Java and worked only after much fiddling with Windows settings and the software itself. One positive though, was the support that Cisco gave us. They were responsive and spent a long time on the phone helping to install the various updates and add-ons required. Ultimately though we just ran out of patience.