David,
I am also into buying my first scanner for 4x5 and shortlisted the same devices as you. To my knowledge the i900 is not available yet and exists only as a press release for download from www.microtek.com.
What I found interesting is that the Microtek nearly doubles the Epson in weight (25.5lbs) and has no glas plate in the scanning path.
I guess we have to wait some more weeks before first hand opinions show up on the Internet.
Martin
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