The lowest end scanner I'd suggest would be somehting like the Nikon LS-2000. It's a few generations old, produces 2700 real DPI, and features Nikon's "DigitalICE," a dust/dirt sensing and removing system. As a 'real' film scanner, it will do better than any flatbed, even the new ones, on the market. You can find a clean used unit for ~ $200 on Ebay.
There are several 4000 DPI models from Konica/Minolta, Nikon, and Canon. Aviod the Pacific Digital, HP, and other 'off brand' options. In this market, the big three produce notably superior hardware.
The curent desktop high end unit is the Minolta 5400. 5400 DPI is approaching overkill. Unless you've used fine grain film, 2700 DPI will get most of the information that is in the film. 4000 gets most of what's left, and only the sharpest images will benefit from a 5400+ dpi scan.
The most improtant thing to look for is infared dust removal.
ICE (Nikon, Minolta) and FARE (Canon) allow the scanner to locate dust, scratches and other film imperfections. Software then fill in the damaged area. While not 100% effective, this will save lots if time hand spotting each mote of dust.
AFAIK, the high end flatbeds are good for ~2000 DPI of real resolution. They offer less dynamic range, and are not as good as a dedicated unit at digging detail out of shadowed areas. Still, a good flatbed may be sufficient for your needs. (Net publishing, small prints, etc.)
Here are a few links...
http://www.bhphotovideo.com/FrameWork/char...lmScanners.html
http://clarkvision.com/imagedetail/
http://largeformatphotography.info/scan-comparison/
http://www.imaging-resource.com/SCAN1.HTM
http://www.filmscanner.info/ (needs translation)
-Greg
