Here's a link to the mouse
that I use. Good for lefties like me! It has the side scroller wheel - which I don't use, because I didn't want to install the 60meg program the came with it.
It only takes one battery. Haven't had it long enough to know about the battery life, but I'm sure it's better then my old logitech. It's rated at 6+ months for battery life.
There's a small USB dongle that plugs into the laptop - it acts as the receiver for the wireless signal. The transmitter is built into the mouse so there isn't anything hanging out. I switched to wireless two years ago and haven't looked back. Batteries were the biggest problem, but they've made huge improvements!