I'm using some Logitech mouse (MX620 I think). Works great for me, super high sensitivity compared to what I used before, and now I get pissed off with low sensitivity, slow cursor speed and low resolution on cheap mice. This one has a laser engine, claims 800dpi IIRC. It's pretty good resolution. Side buttons are nice (forward/back, also extra mouse buttons), "search" button is *Can'tSayThisOnTV*ing useless and annoying and I turned it off (unfortunately cannot be a sixth button). Adjustable scroll wheel, looks like it has a pretty wide range but really it's ultra-smooth or clicky, no in between. Ergonomic shape, comfy enough. Cordless is nice, doesn't cause problems if you keep the batteries fresh and the receiver close. I like it a lot, but I take it you want something more hardcore and gaming-oriented.
Tl;dr? MX620 is a good mouse and I love mine but probably not hardcore enough for you.