I purchased this mouse to replace my trusty Logitech V270, which has served me brilliantly over the last 4 years.
Having recently switched from a PC laptop to Mac, I was looking for a mouse of the same size and style as the V270, but without the fuss or fiddle of a USB dongle.
As with the V270, I find the M555b to be both practical and convenient, with excellent battery life.
It's comfortable too (even with large hands like mine!).
The mouse works well with Mac OSX (Leopard) Spaces etc... but you will need to install the Logitech software to make this work.
Whilst it is expensive, I use my laptop all day long, so the saving on batteries more than compensates for the price premium.
Overall an excellent product, and a worthy replacement for the V270.