I bought the MicroTek 6800 a couple of months ago and LOVE IT!
The software (ScanWizard 5.821) is a tad unstable. It crashes every half hour or so, but restarts easily. It's a bit poorly conceived for mass scans, forcing you to go to the mouse where hot keys would be more convenient, but the feature set is GREAT.
The scanner itself is fantastic. I'm nearly 1600 scans into a project with a long way to go, and couldn't imagine doing this on my old scanner.
This is my second MicroTek. The first one's still alive and kicking - I simply needed more speed and features.
Your mileage may vary....