Switched to AAISP after 10 dreadful months on BT "broadband" services (56K-like speeds).
During those 10 months I've had 8 BT technicians trying to address the problem with no success and uncountable hours spent on the phone with them without improvement.

After switching to AAISP my connection went flying to a real 10Mb/s (sometimes even more) with great latency, which is as good as it can get on the Isle of Dogs/Poplar where I live.
Their Customer support had been excellent so far, their notifications, logs/usage statistics, account management pages and wiki are very well organized, comprehensive and informative. I particularly love their text messages notifications that will let you know straight away if there is something wrong, since when and how long it lasted. They even have a map of storms around the UK possibly affecting broadband lines.

Would definitely. definitely recommend them to anyone, especially if you've been having issues with your current ISP.