Quick answer: yes, it's the best for OS X.

--The gnutella network is big and is growing. I'm watching for when it hits 2 million online users. If you go to http://www.limewire.com/english/content/uastats.shtml, you can see the clients that are connected. Of the ones that can be run on OS X, LW is the leader. New vendors are often just LW "under the hood." They take LW's opensource code and tweak it, but then they can't keep up with LW's 5 years of development experience. Lot's more to say here, but no more time

btw--did you try clicking the Lock icon on your OS X Sharing Preferences to get at the Firewall settings?