Same here with my 23".
I use to run at 5700 DPI at all times when I had my razer naga (POS mouse build I was using it and all of a sudden the right finger didn't work. Turns out it snapped while in use lmao) and just turned down the sensitivity in the menu 5700 DPI was perfect for every task in BF3. Vehicles, on foot, sniping, you name it.
Now I'm using a mx518 that I bought back in 06 lmao. its sad that a $50 mouse that is 6 years old has held up to more abuse than a $120 mouse that was 2.5 years old.
However going from 5700 DPI to 1600 DPI was a huge jump along with the laser to optical. I've been able to get it quite close to the speed and precision of the naga, but a G700 is in my sights now.