Summary: If you already have an Epson Perfection 4490 Photo scanner, then you might as well get this if you plan on scanning lots and lots of documents. However, if you don't have the 4490, then just get one of those new multifunction scanner/copier/printer/fax machine things that has an automatic document feeder, as this accessory alone costs as much as a cheap multifunction.
The next problem is the complete lack of documentation. It's not exactly hard to figure out how to install the ADF, but it would be nice if there were more than just a warranty slip in the box.
Also, the software is completely incapable of handling double-sided documents! This is extremely annoying. After scanning, you have to sort the pages manually using tiny thumbnails that are impossible to distinguish from one another.
Aside from these limitations, the ADF works pretty well and has made my life easier. This huge stack of documents waiting to be scanned for years will be gone in no time!