I have been with them for four years or so, but only have experience of them in a non business account. But for me they are excellent, and I cannot recommend them highly enough.
The employ traffic shaping, which gets most of the p2p people to use different isp's. That way most normal surfing through their network is fast.
P.S. If you do go with them, can I be cheeky and ask to be your referrer? my userid is RCCLTD. thanks.