You can get Mactella from http://www.cxc.com.
I haven't tried it, I run windows & linux, so I dont know what its like, but it might be better than what you've tried.
If you dont like Mactella and want to wait for something good to come out, Bearshare is rumoured to be releasing a Mac version sometime, not sure when though.

Hope that helps you,

- Tommmo