I'm afraid, no matter what they say - iMesh does include Spyware, Adware, Viruses and trojans... and further more, lowers the overall security of your system.
WinMX, ok if you must... but it still includes viruses.
Any p2p system will be harvested with viruses, no matter what. Even if you have antivirus, are you sure it has 100% detection - I think not!
No antivirus can detect 100% of all new viruses, so you could become infected - and not know it.
IMHO, stay away from all p2p systems.