my g100s does some weird malfunctions on lower senses like 40+cm/360, some times it just goes to negaccel, no matter how fast i drag the mouse. I'm using it on 400dpi with about 30cm/360 sens nowadays, no issues this way.
It might just be me, but i had to replace the mouse 2 times already in 6 months, because the microswitch on the LMB had the double click/missed click issue (which isn't an problem with logitech, they don't make a fuss about replacements, but still... it's supposed to be some high quality 20M rated omron shit, yet it broke faster than in any other mouse i had). Solved this by buying a 10pack omron replacement switches from china (10$ with shipping) and now if i have any similiar issues, ill just replace it myself.