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I'm in the market too, but can only recommend against Kaspersky for Mac. While their Windows product is among of the best, their Mac product has severe issues. In addition to a significant performance penalty, the software often locks the machine hard during shutdown or restarts. It sometimes truncates files that were open near shutdown time, causing total data loss.
This is reproducible with a virgin Snow Leopard or Lion install on multiple macs. Kaspersky acknowledged the problem in their forums as early as November 2010, repeatedly promised fixes, then eventually simply removed the posts about the issue. When I last tested in February, the issue still stood.
Of interest, you'll find similar shutdown complaints against the free FlashBack removal tool they offered, as well as the minimal Anti Virus scanner they offer in the Mac App store.