I have Freesat HD here in Anglesey and the signal strength is always 100%.
I got it because the Freeview reception I had was rubbish, and that was with three boosters fitted.
You don't get as many channels with Freesat - unless you do a manual tune which finds in the region of 400. Most of them you will not want to watch!
I know a few people who have Top-up TV and, since I've never heard them complain, I can only assume that it works well.