seeds = people with the whole file
peers = people still downloading the file, but sharing their completed chunks of the file.

Having a LOT of peers and very few seeds is NOT a bad thing if many of the peers are mostly done and/or they tend to have vastly different parts each.

A MAIN cause of slowdowns is MOST users are FIREWALLED and can only download from NON-FIREWALLED users.

If there's 100 people and 80 of them are firewalled, and you're 1 of those 80 then you can ONLY download OR UPLOAD to the remaining 20 people. This means ALL downloaders are fighting over the upload bandwidth of the very few non-firewalled users (which in this case there's only 20) while those that aren't firewalled can download from anyone who has a piece of the file they're missing!