I'm on Be, been with them for almost a year now, never had any major outages and the speed is good. I'm about 1km in straight line away from the exchange and I have 12mb downstream. I have bad phone lines and I'm running through an extension too, so I'm sure with fiddling around I could increase my speed.
A word of warning, the BeBox is not very good, it crashes fairly often (at the very least once every 3 days generally) and takes a couple of minutes to boot back up but it's not a massive problem.
Overall, I recommend their service. I could refer you too, and you then have to pay no connection fee, and I get a month free