I love my MX518. Felt huge at first...but after about a week, I was used to it. I don't go up to the full 1800dpi (usually only 1600-1700dpi). It's quite a nice mouse.
it has the same dpi setting 400 800 and 2000, and you can use the software to choose a setting anywhere between those and assign it to the dpi buttons.
then main difference is it's cordless, but it performs just as well.