Tracking
Like just about every mouse short of the Boomslang, the Wireless IntelliMouse Explorer relies on optical technology to track mouse movements. Early optical tracking technology wasn't fast enough to keep up with lightning-fast twitch movements, but the Wireless IntelliMouse's optical sensor has no problem keeping up with my reflexes. I've never been much of a twitch-gamer, but for what it's worth, I don't notice any tracking latency difference between the Wireless IntelliMouse Explorer v2.0 and my wired IntelliMouse Explorer 3.0.

But just because the Wireless IntelliMouse Explore doesn't have any perceptible tracking latency doesn't mean that the mouse will instantly respond to every twitch. The mouse has aggressive power-saving measures that drop the sampling rate significantly after just a few seconds of inactivity. Moving the mouse or clicking any of its buttons will bring the mouse out of its power-saving state with a slight but noticeable delay.

The Wireless IntelliMouse Explorer actually has three sampling states: active, idling, and a dormant mode reserved for periods of inactivity 10 minutes of longer. As long as the mouse is in its active state, there's no latency to worry about. However, the latency associated with bringing the mouse out of its idle state is something fickle enthusiasts will no doubt notice, especially while playing games. In first person shooters where campers snipers may keep their mice still for a couple of seconds at a time, the latency penalty associated with bringing the mouse out of idle could be the difference between a frag and a death. I can just see online gamers whining about "mouse lag" in Desert Combat and Counter-Strike.

Software
There's more to the Wireless IntelliMouse Explorer than hardware; the mouse's driver is packed with features without being bloated.

The Explorer's five buttons can be bound to a wide array of functions that go above and beyond the usual defaults. Buttons can be bound to Windows commands like cut, paste, open, new, minimize, maximize, and undo, among other functions.

Users can't bind wheel functions to anything other than scrolling in Windows, but there are plenty of ways to control how quickly the mouse scrolls up and down. A huge range of vertical scrolling speeds is available, and the mouse also has an adjustable accelerated scrolling feature that kicks in during repetitive scrolling. Using accelerated scrolling feels almost like winding the wheel up with each flick, and it really speeds up scrolling through massive documents and long web pages. With seven different acceleration levels, it's easy to customize the acceleration to suit one's particular needs.

Acceleration isn't available for the tilt wheel's horizontal scrolling capabilities, but users can still adjust the horizontal scrolling speed. A total of ten horizontal scrolling speeds are available, but they're a little on the slow side for my tastes. The slowest speed barely moves at a crawl. Te fastest is quite a bit quicker, but it doesn't compare to the mouse's potential for blistering vertical scrolling speeds.

Microsoft's driver also includes handy battery level and wireless signal quality indicators. It would be neat if the battery life indicator could estimate how many days (based on average usage statistics) were left in the mouse's AAs. Maybe in the next version?

Even better would be control over the mouse's idle state. It would be enough for Microsoft to let users dictate how quickly the mouse drops into its idle state. At least then gamers could choose to sacrifice a little battery life to eliminate the mouse's only latency-related flaw.