You're right - there are heaps of spam files on the network now. Also heaps of infected files. LW's just one Gnutella client...if you're not happy with it then you could try some different ones (if you like). The links below are to good, free clients.
BearShare

Phex

FrostWire

If you're going to be downloading program files, you need to be really careful...zip, exe & rar files are the most likely to be infected. My best advice would be to stay away from programs - even if a file is clean, chances are that it won't work properly as you'll need a code/key to use the program.

If you do want to take the chance, make sure that you're using a good AV program. Keep it updated & scan every file that you download...before you open it! Even if the file has a good Bitzi rating, still scan with your AV before opening.