With 3200dpi gaming mice becoming de rigeur, Razer needed to step it up to 4000 to keep the pissing match going. Even though a 3200dpi mouse is already too fast for some, I4U's reviewer says that Razer's 4000dpi Lachesis "is very accurate and tracking is great," particularly in Crysis. But, most of you probably aren't twitching around a 30-inch screen like the reviewer.
If you're on a considerably smaller screen, you'd probably find yourself in the case of the missing cursor. Fortunately, you can adjust the resolution on the fly, and profiles are stored in the mouse's 32KB of onboard memory. The major drawback's actually the scroll wheel, which he wishes was more like the one on Logitech's G9. That aside, it pulls a pretty solid 9.0 rating.
Since it's an ambidextrous mouse, I'm also guessing dedicated-hand diehards (like myself) or un-fans of Razer ergonomics might not be entirely comfortable with it either. At $80 MSRP, I'd grope one in-store somewhere before dropping coin. [I4U, Razer]]