This is indeed puzzling. Firewalls are supposed to be hard to download from. Since most here know this, I think they stay away from them and go for the normal, or black colored, ones. Consequently, firewalled clients have transfer slots available more often since people don't want to download from them. I have found good results with firewalled clients as well. Some firewalled clients are horrible at uploading materials, but many people change the firewall settings to permit LW to run or force their computer's IP address.

I don't really know how the whole quality indicator thing works. It works ok for me, but there are several times when I find a 4 star client refusing a connection and 0 star client giving me instant connection and excellent speed.