In the FWIW department, I just last week asked my photo instructor this very question. He is the department head responsible for specifying what equipment the department gets; and he also works outside the college as a consultant to companies to help them set up their own in-house digital photo labs.
The school has a few of the high-end Imacoms, and these are likely the best bet. But I can't afford that, so I asked him what he would recommend for under $1000.
He said he just bought four Microtek 120tf scanners for the school. These retail at about $1800 - they are dedicated film scanners.
While I was surfing the site I also noticed cnet liked the Microtek i900. At $600, I like it better, too. This is a combination flatbed/film scanner - it has a drawer under the bed that you can pull out and put film into for direct scans, rather than through the glass.
Lastly, a guy demoing equipment for Mamiya at our school said he just bought an Epson 4870 (retail about $400) and recommends it for film scanning.
All the above support the digital ICE technology.
The reason this is a FWIW, is that I know absolutely nothing about any of these myself, other than what I've read on the company websites (and CNET's review).
I am curious, tho, that no one on this thread has mentioned any of these, which leads me to believe that a) they are not the level of gear people here demand, and don't compare to the Nikon and some of the other ones mentioned. Or they are newer than when people here last bought a scanner, so perhaps they are not familiar with them.
Any input on that front would be helpful, as I, too, am interested in scanning film up to 4x5, and intend to focus on b+w, but also do some color.
Thanks for the interesting posts.