Nice review. I'm currently using a Copperhead, Razer makes quality mice. Also, they all glow like Tron, which is just awesome.

I find that Razer mice are ideal for RTSes. In those games, you're constantly making fast moves and the downward shape of the mouse buttons help, even if it's a small factor. They're also smaller on the bottom than at the top, making them easier to flick with your wrist. I've used Logitech mice for the majority of my time, but I find their semi-circular designs aren't too comfortable for the long run.

What do you think of the Microsoft Habu that Razer helped design? I know it's a little old, but it looks great.

But is it worth upgrading from another mouse?

Like a mx518

Or a G9

Depends what you're using the mouse for. The G9 is great for FPS, better than any Razer mouse, IMO. If you have a 518, I think it's worth upgrading to an Imperator. That thing looks sweet.

If you play MMOs, get the Naga. My friends who use it for WoW only need to use WASD, alt/shift/ctrl on their keyboards. The Copperhead is great for RTS, for the reasons I mentioned before. I would've gotten the Krait, but it lacks the side buttons that help in browsers.