Lexmark may not be the first name you think of when you consider purchasing a new printer for home or at work. They are not what I would consider to be one of the "big names" in printer. People normally think of Cannon, Epson and HP.
However, this is a very robust manufacturer for office and home printing solutions, if a little expensive on consumables.

Looks/ergonomics.
the T640 is a direct replacement for the T630 which in turn has been direct aesthetic decendants tothe T610 range. They all look the same and all seem to perform the same until the T640. It now has lost its contoured curved look and gone for a sleek, angular design. The basic layout remains the same.
The front of the printer comprises of the Paper feed draw that is built in and can take up to 200 sheets of paper, as well as the drop down Paper/Envelope feeder. This in turn is linked as a "double door" layout to the control panel which is liftable to access the Toner Cartridge.
Still with me? good!
The beige drabness of the casing has in some way been replaced with charcoal grey sides but retains its colouration on the front, top and back.
On/Off switch is recessed and towards the rear on the side. This can be a right pain when stacking 1 printer next to another. Power Sockets are also access from the side and need a 90 degree plug to allow printers to stand side by side.
Network connectivity is built in to the printer thus eliminating the need for Jet Direct boxes to put it on the network.

Speed/Print Quality.
Dont forget this is a MONOTONE printer so it is not going to produce colour documents. However the speed it is able to print letters is amazing. It almost spits the pages out and at a fantastic quality. Only downside is it still suffers the uneven "graining" of print when the toners are running low. You do get a warning but can end up with printless stripes down your pages. We use them for producing large multi page documents for clients and these are always crisp, ledgible and fast!

Expansion.
2 Great additions are available for this printer. 1 of these i feel should be included in the printer itself as most of the competitor printers seem to offer this built in. A duplex unit can be purchased for £150 that sits either under the printer or between the printer and the expansion draws. It is a matter of placing the printer on the duplexer. No screwing or drivers need installing. This works well for double sided documentation if a little noisy.
The other essential addition for our office is the abilit to add an extra 2 paper trays to the printer. These can be either 250 or 500 sheet trays and again just allow the printer to rest on top. The in built mechanism allows the printer to pick up paper from these trays.