Been with 3 ADSL ISP's since our exchange was enabled a few years ago.
Pipex were first and they were OK really, I understand they are capping and throttling now though? I then switched to Plusnet after advice from friends, this was before they went downhill late last year, worst move I ever made.
Now with Zen paying £30 per month for the original no caps, unthrottled 1mb service, and its very quick and ultra reliable, so much so I'm tempted not to ever bother with capped MaxDSL. I can download well in excess of 100 gig a month with this account if I want to, MaxDSL looks like its pretty flakey for a lot of people as well, even after the 10 or so days.