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I got a Logitech MX310 for my birthday last year. I had planned on getting the MX510, but it was too expensive. The MX310 is a decent mouse. It's a USB mouse, and of course came with the increasingly-unnecessary USB-to-PS2 adapter.
As most of Logitech's mice do, the MX310 has extra buttons beyond the usual two plus scroll wheel. It's got a "Quick Switch" button beneath the scroll wheel, and Back and Forward buttons on the left and right sides on the mouse. They are a bit awkward to use; the Quick Switch button is too far back (towards you)--it requires bending your middle finger a lot. It would be better if it were in front of the scroll wheel instead. The side buttons are too far up; my thumb and pinky finger tend to rest in the indented sides of the mouse rather than on the ridge near the top where the buttons are placed. They would be better placed lower down on the side. The Forward button (activated with the pinky finger, for righties) is also a little too far back on the mouse, like the Quick Switch button. It is probably a non-issue on the higher-end mice, where the Back and Forward buttons are larger and placed beside each other on the same side of the mouse.
As far as I can tell, the resolution of the mouse is nice. With a bit of fiddling (specifying a USB product ID) with lmctl, I can change the DPI of the mouse to 800 rather than 400. It's very sensitive, and I haven't yet found a material on which it has trouble tracking. (I haven't tried anything absurd like a transparent glass desk yet.)
All in all, the MX310 is a decent mouse, but you'd probably be happier with one of the higher-end ones, since they're more ergonomic and covered with a more comfortable rubber coating instead of the plastic that coats the MX310.
