Just to put my
in...
I've had two dealings with spamcop, but never any problems.
1) Someone spammed with a list of webcam sites, mine was one of them. I never figured out who did it, or why. Spamcop marked it as a joe job/colateral damage without being anal about it. I think I'm still in SPEWS as there are a lot of real spammers in the same IP block as that server.
2) As the listed contact of an IP address range I was auto-emailed a complaint about a spam that had originated from a PC on my network. It turns out it was a W98 machine that had been IE exploited with a proxy trojan. The damn thing was fully patched, but IE is still full of holes. I wouldn't have known about it if I hadn't received that complaint.