Different strokes for different folks.

Probably 60% of my
ebay feedback is as a buyer. As a buyer I *MUCH* prefer Buy It Now/Best Offer listings to auctions. You get the best steals and cherrypicks on fixed price listings. If I see something that the seller doesn't realize he has, I can swoop in and grab it. With an auction, I have to worry about who else might also see what I'm seeing.
Also, with fixed-price shopping, it's much easier to allocate/budget money. I know pretty much all the time how much I have spent or will spend. With auctions, I have to budget based on my maximum bid/snipe, and may end up passing up on something only to not end up winning the other auction anyway.
My buying is probably 90% Buy-it-Now or Best Office, and 10% auction.
As a seller, with auctions you are maximizing your upside potential, but with fixed price you are minimizing your downside risk. You won't get the moon money when two bidiots decided to duke it out, but there's also no chance that you'll be buried just because you happened to run your auction at the wrong time or when the wrong people were browsing listings.
I'll take the latter over the former all day long.