i have just switched from BT to Sky... and I have to say that it has gone better than I anticipated. I should mention that I had no problems with BT at all - the decision was purely price.
I placed my order on 23rd April (2008) and received a letter saying the estimated date for activation would be 2nd May.. and it was activated on 2nd May.
I couldn't connect at first using the ethernet cable connected to the router, so I checked my "network connections" and noticed it was disabled, so after enabling it I was able to connect without any problems.
I have a few laptops for the kids in the house so I then had to get the wireless connection to work. The sky router is defaulted to WPA-PSK encryption and comes with a little card that tells you the key. The problem I had is that my ASUS laptops are 4-5 years old and I had been using WEP encryption to connect to the BT router.... and the laptop uses an ASUS tool which would not give me an option to set WPA-PSK encryption on the laptops.
Before I tried to sort out this security problem I first tried to prove I could get a wireless connection, so I logged onto the sky router and selected the "disable security" option, and I was reassured to find that I was able to connect wirelessly to the internet. Then I needed to put security back on. From reading various forum postings I could see that Sky seemed to be referring customers to manufacturers for any wireless connectivity issues, so I took the easy option and logged onto the Sky router and changed the security option on the router from WPA-PSK to what I had used with BT, i.e. WEP... and thankfully the wireless connection with WEP security works fine for the laptops.