99.9% of the time I will not bid on an eBay auction if I can't pay for it with Pay Pal. IMHO sellers who do NOT accept PayPal are shooting themselves in the foot and severely limiting their sales. PayPal is becoming a base technology or in other words, something you have to have or you won't be in business for very long if selling on eBay is your livelyhood. Again that is my opinion so take it for what it's worth.
As for personal checks; I take them and I put a warning in my auctions descriptions about how I will "hold merchandise until check clears," etc, etc. But I feel that that is enough to discourage people from mailing me a bouncy check.
Cheers!
Bill