The i900 has been replaced by the M1 (F1 in Europe). The M1 adds a rather clunky focusing system that takes a long time to work and is inaccurate about as often as it is accurate. Make sure you understand that after the 1 year warranty is up, Microtek does not repair any scanner. They will give you a coupon for a relatively small discount on buying a refurbished unit from them.
The current group of moderately ($250 to $1000) flatbeds have pretty much maxed out the potential for flatbed scanners in this price range, so there isn't a whole lot of difference between them in terms of optical ability/performance.
Doug
