I changed phone line, broadband and talk package to Sky. They did everything I wanted on the day they said they would without any problems whatsoever and I kept my phone number.
On the very rare occasion that I have required assistance since the change I have had first class help from English speaking people in the UK.
About a month ago I had a problem with my phone when it didn't always connect. After contacting Sky an OpenReach technician attended by appointment (on time) and to make sure everything worked ok he changed the cable to my house and the junction box inside. He remarked that even though he worked for a branch of BT he wouldn't touch their BB with a barge pole. He also commented that of all the different ISP's that used OpenReach Sky were the ones that wanted to get things fixed asap without any problems for their customer.
Don't worry - no pitfalls.