Logitech VX nano here, it's perfect for my needs and the small USB dongle means you won't really notice it.
Programmable buttons too.
I've got this too... fantastic mouse. Decided i liked the ability to plug it into any pc i wanted (rather than just bluetooth equiped ones) especially with the dongle being so small.
Trouble is, i have read LOTS of bad press about the logitech software so have been a bit nervous to try it? I am currently using steermouse on the trial.