Richard,
Can I reply to your question with my own question? I too would like to know how this leaf node vs. ultrapeer thing works!

Before you ask: Mac OS 10.1.5, LimeWire 2.7.9 Pro, Cable connection @ 3 MB

Everytime I have ever run LimeWire I have always been a leaf node. Today I started LimeWire and I guess I am an ultrapeer? I say this because that is what it says on the bottom of my Connections Screen and I am connected to numerous Hosts(maybe 60?), whereas before I was never connected to more than 4 !

I have not changed any settings or preferences. I am sharing 1 or 2 more files than I was before for a total of 16 shared files. Is leaf node vs. ultrapeer based on the number of files shared and I have gone over the magic number, or is it based on connection speed, or what?

Thanks, Steve