I'm on SBC-Yahoo!-DSL and I generally get good performance out of LimeWire PRO. Except that IP Direct Connect is sorta tricky and poorly documented... LimeWire is cross-platform, Windows, Mac, Linux.... nice!

Shareaza is OK. I use it for BitTorrents. IN general, if the file you want is popular, LimeWire is good. But Shareaza uses more networks so maybe you can find more stuff...

In my experience (2 years LimeWire PRO, 6 months Shareaza) usually LimeWire is faster than Shareaza...

Good info here for config + troubleshooting... why doesn't LimeWire document like this? :
http://wiki.shareaza.com/static/FAQ.FirewallsRouters

I'd like to hear more from anyone with multi client experiences?