"Best" autofeed is a problematic issue. Best for what kind of documents? In what price range?
At my job, we use the older version of the
Fujitsu fi-6770 for a lot of our scanning. (Ours have a 5 prefix instead of 6; they're not on the website. I don't remember the exact numbers.) We often scan a few thousand pages a day--we need high speed, multi-function, compatible with scanning database software scanners. They run somewhat more than $5,000... I doubt that's what you're looking for. (It's a great scanner. I've been spoiled by working with scanners that scan 60-90 ppm; the little all-in-one fax/copy/scan machines seem horribly slow.)
If you know what you'll be scanning (pages from binders, paperbacks with the spines cut off, textbooks with the spines cut off, whatever), mention that, because it'll help people recommend scanners that work for the documents you have.
Some small scanners won't deal with anything more than 8.5" wide, which means they can't deal with many textbooks. Some won't work on postcard/photo sized docs. Some won't scan duplex, or do so incredibly slowly.
Mentioning the content you'll be scanning, the OS of your computer, and any relevant details will help. (E.g.: "it needs to be portable so I can drag it from home to office" or "needs high DPI option for scanning business cards & small photos" or "needs to scan paperback pages well, so must have paper guides for small pages.")