When I first joined Sky there was no line to my property, took 3 weeks to get the line up, I've just moved and took 2 weeks to swap over... You should see very little in the way of downtime though as your migrating, if you have a little bit of overlap a few hours tops.
Speeds on the whole are top notch, at least here on the Whitstable exchange, I get a full 20Meg connection and see throughput that matches that practically all the time. Have seen some slowdowns now and again but nothing that would make the connection unusable, to be honest I only noticed coz I was throwing some big files about for work, browsing you wouldn’t have noticed.
CS have seemed reasonable the 2 times I have called, you do read some horror stories though as you do with all ISPs.
The router supplied is OK I suppose, seems stable enough, a bit light on “Advanced” features but if you need them there are ways to setup your existing equipment for use on the line, there seems to be some debate on this contractually, my understanding is that its tolerated but not supported…
Sky Anytime+ is fantastic even more so if you have the movie packages