Personally I use a combination of Phex, LimeWire for music, & Azureus for other items. Though even better options are available via torrents such as lossless music on occasions. I use Phex because it reaches other gnutella program clients not only LW users. Whereas LW mostly only finds & downloads from other LW users. LW also greatly biases Uploads toward other LW users, which is unfortunate since there are so many other gnutella programs & users out there. So Phex is great for those harder to find files in particular.

For torrents I definitely favor Azureus (mac/windows), though there's other good ones out there for Windows users too.