The Zen line in particular is very stable...
I've got Zen at home and it's absolutely rock solid. Not the cheapest provider but you get what you pay for IME.
I've had a couple of instances where it has failed. Their support is great until they inevitably say "everything's checked out fine our end, we'll raise a fault with BT" whereby it's a week before anything happens. On both occasions it turns out some muppet unplugged the line from the DSLAM at the exchange. I guess that's the same for everyone who relies on a line that terminates in a BT exchange though.
Kevin
Used to use Zen, we're very reliable - did find them expensive though. Changed to uk online and had an average of 22Mbits (yes 22) we were only 200 meters from the exchange
Moved again now, out of range sadly, so now on Pipex 8MBit which I can say is very good, hasn't died on us yet in 5 months. We've got a belkin wireless router with adsl modem in it, link to 1Gbit switch and from there we got 3 pc's plus the server on a pretty speedy 1Gbit network.. I access internet with the laptop via wireless directly through the belkin..
I managed to get Micro$oft Partner status through work, so naturally its all vista ultimated up, apart from the server which I've left 2k server on as I doesn't do much, more of a NAS these days - and my laptop which has the vista business varient...
All in all it works very well...
Chris.