The 3.5G's sensor feels better than the 3G's one. Don't know why people say otherwise.
The 3.5G sort of reacts faster to tiny movements, just like the G400, compared to other sensors.
I actually think it's the best sensor around. Didn't like Roccat's 3360; didn't like Zowie's sensors, except for maybe the FK's, which I guess is placebo because of the shape; didn't like the MTL04; didn't like Ninox Aurora's sensor.
I used all of them, except for the MTL04 and Aurora, at 1800 dpi.
Donkeys cursores, my frrrrrrriends.
I also didn't like Logitech's 3366