hi mtbiac
i have a t40p and i bought the logitech mx900 and the m$.
common pro's:
both are working out of the box, real plug'n'play
activate bluetooth and pair the device
you have no cable and both are optical mice
common con's:
both must have batteries and you can feel this!
not that precise as the usb optical mice
first, i tested the m$ mouse. cool design, cool feeling, cool additional mouse buttons - but no fun when it comes to precision. playing d3 with that mouse won't be fun!
the logitech feels less comfortable, got more buttons and doesn't look that good. the precision is quite good, but optical usb mice are still the best when it comes to d3 .

(currently using the m$ intelli expl. v3)
if you love the feel of these m$ mice then buy one. if you don't like a jerking mouse, don't buy the m$, buy the logitech instead.
if you don't like the heavy weight, save your money and take the usb optical mouse.