An excellent mouse overall and part of the MK850 keyboard/mouse combo. The cheapest it has been in a little while, though not the historic low.
Uses a single AA battery which lasts for ages (up to 24 months as per Logitech). I have one and like its overall size (not too big or small), weight (on the heavier side), build quality (well made, soft rubber surface) and responsiveness (no lag via dongle, no dropouts). Good for working from home.
Currently $69 from Bing Lee and $89 from JB Hi-Fi/Officeworks
I've had one of this for nearly two years from a previous deal for about the same price. So far so good. I felt of a lot drifting since Logitech abandoned their true laser lines. This one is relatively bulk in size but has been reliable for most surfaces I have used.