Yeah, we are slightly offtopic
I tried various mice this year and I finally stick with the MX510. Highest resolution for optical mice, 10 freely configurable triggers, 3 years warranty, decent ergonomics and fair price.
Together with a rough glass mousepad I'm absolutely happy.
In case you prefer wireless (which I don't ) the new MX1000 is probably the best choice. For lefthanded ones the MX310 is worth a look.
I would expect a succeder of the MX510 (Logitech's gamers mouse) with the new laser sensor, improved precision and a four direction wheel by the end of the year. If you're not in a hurry it might be worth waiting.
... and in case you ask: no I don't get paid by Logitech
In fact I had a MS mouse before but sensor and button quality isn't up to par, the newest drivers don't allow full customization, warranty is shorter and I don't feel like filling Bill Gates pockets