When you see a scanner with a 50-sheet, duplexing ADF built into its top cover, as with the HP Scanjet 5590 ($399.99 direct), it's a safe bet that it's designed to scan multipage documents for OCR and document management applications, as well as fax and copy.
50-sheet, duplexing ADF and 35-mm transparency adaptor are standard; Handles OCR well; Better slide scan quality than most flatbeds
No batch scanning; Transparency adaptor is external, rather than an integral part of the unit; Lacks feature for removing scratches or dust from image