Canon DR-2580C document scanner
It goes for $644 at scantastik.com. Mine arrived two days after I ordered it (shipped from Pennsylvania). It was easy to set up, and the software was fairly easy to use. The unit is rated to scan 25 pages per minute at 200dpi in black/white mode, but 1) it scans both front and back at once and 2) it scans at 300 dpi, both with zero speed decrease. (It also can scan in color, though at a significant speed decrease.)
What's great about the scanner is that it just works. You load up to 50 pages into the document feed and just let it go. Two minutes later, you load another 50 pages an hit continue: the software appends the new pages to the ongoing PDF file it is creating.
The software can detect page orientation, and it can detect blank pages (so you can load single-sided documents along with double-sided documents and it'll figure out what scans to keep), but I turned off all those features because they slow down the scanning. Instead, I am using Adobe Acrobat Standard (version 8 is bundled with the scanner) to post-process the files---Acrobat detects orientation and does OCR on the pages to enable full-text search. The full-text content is kept as an invisible overlay on the original image, so all formatting and images remain. This processing goes slowly---it takes 2-4 seconds per page on my 3GHz, single-core Pentium 4. But it's not a big deal because I just batch the jobs overnight.
The system has an ultrasonic multi-feed detection system which determines with very high accuracy when the paper feed system sucks in more than one page at a time. I found this happened about three times in the 10,000 pages I scanned.
Not everything is perfect, though. The document feeder is not all that good at keeping pages aligned perfectly as they go into the scanner, so the pages tend to come out somewhat skewed. (I think Adobe can correct this in post-processing; I'll have to check it out some more). And feeding in spiral-bound reading packets can be difficult: hole-punched pages can get caught on one another, causing severe skewing and mis-feeds. I found a way to finesse the feeding process so the pages untangle themselves, but it involved my actively attending to document feeder as it scanned.
At $644, I think the device is a great deal. The only consumables with this scanner are the rollers in the document feeders, which must be replaced after every 10,000 pages: this costs $50. The main thing I'd want to improve is the alignment on the paper feeding. I expect the Xerox Documate 252 is the closest competitor to the Canon---it's also a 25 page per minute/50 images per minute document scanner. It costs $100 more at scantastik.com; if it has a markedly superior feeder, that might be worth it. Keep in mind, though, that the Canon is very compact and weighs about four pounds: you can easily carry it around. If portability is at all an issue for you, the Canon is the obvious choice.
PS: I found I could successfully load 100 pages into the paper feeder (double the rated amount) with no troubles, as long as I actively attended to the feeding process to ensure skewing was at a minimum....
