will you be making prints of these pics too?
if you like to scan regular print matter and spend less than $300, I recommend Epson 1200 series scanners. many come with a transparency adapter built in. It's fast and you can get an Epson Twain beta for OS X download from epsondevelopers.com although it's not officially out. It works with my 1200S SCSI scanner even.
-dw-