I switched my phone & ADSL from BT to Plusnet this week.
All in all a positive experience. I was kept informed all of the way, received the router in time, was disconnected by BT a day before I was due connection but managed to get Plusnet to bring the activation forward so I was only without connection for a few hours. Early days but connection is good & speed higer than with BT (?? go figure).
Only downside is the router settings page wasnt working correctly (though working ok), may have needed a reset but I switched to my old homehub instead.
So with the cashback & 18 months free deal I'm more than happy. Bonus is the member center is more user friendly than BT's so actually usable & this forum is great for support. Long may it continue.