multiple pages of documents
If you're doing large documents frequently, consider a scanner with an Automatic Document Feeder (ADF) such as the HP 5590 (or the 7650 if you're scanning legal size paper). This may double the price and the source document may jam if its not "clean" (no rips, dog ears, staples) but worth it if you need to scan 10 or more pages daily. I figure about 30 seconds per page when I have to manually load multiple pages. That gets old in a hurry.

As for ease of use, I don't know of any scanner that has a significant advantage. If you're only scanning standard size documents, in monochrome, it should be load source, push a button, and you are done, with nearly any scanner on the market. Most even have an email button which will attach the scan to an email document (although this will require some initial setup to specify your email program).