I'm with supanet and last year they were very poor - over the Christmas period (especially) - I have 1mb broadband and was getting something like 48k speed if I was lucky - they did however point out that this was because they were upgrading their piping/bandwidth etc. and to be honest im now finding it good, speed is good and no download limits - at that timet here were loads of threads on Digital spy forums etc, giving them a right slating.
Speaking personally though, im happy enough with them (at the moment anyway)