Switched to Sky via Quidco about 9 months ago. I got their broadband, plus talk service. The broadband speed was comparable to BT, but 'unlimited' for the same price. Include the £95 cashback and £25 M&S voucher, it seemed worthwhile switching. I am still waiting for the cashback, with no sign of it being confirmed, and since switching over, Sky have increased their line rental. All in all it wasn't really worth the bother.
After posting this review, Quidcare got in touch and managed to sort the payment out pretty quickly. Changed score to reflect this.