The top sign of a crap ISP is that they 'traffic shape'. They snoop into what you are doing and make judgements based on their accounts 'last airline magazine article read' and then implement them.
So a very good ISP - for instance BE/O2 - can be turned into a very bad ISP - by simply snooping on your customers and 'traffic shaping'. They will bleat 'Oh yeah, these nasty P2P people are consuming all the bandwidth, so we'll make everyone suffer'. And sometimes they'll hit something important like port 1352.
One way to find out if your ISP is a cock is by running 'TrafficShaper'. It'll show you if they are.. Even if they claim they're not.
In my case O2 had to admit they were traffic shaping as they destroyed bandwith for everyone for months. So not only snoopy cocks, but incompetent snoopy cocks. Nice.