This post at the excellent HackADay web site discusses how the security of wireless keyboards has now been compromised. This makes it even easier for hackers to capture passwords and other information you type on your wireless keyboard. They don't need to risk physical access to install a hardware keyboard capture device or install software to perform the same function. They just need to set up a sniffer device in close enough proximity to capture your key strokes. Under ideal conditions, wireless devices can transmit far beyond their stated maximum range.
I personally use a wireless mouse, a wireless Apple Mighty Mouse which I love, but not a wireless keyboard. I see little benefit to getting rid of the wire on my keyboard since I don't need my keyboard to move so the wire never gets in the way.
Good luck to any hackers who want to derive meaningful information out of my mouse movements and clicks. Without knowing what's on the screen at any given moment, that information is next to useless. I know it's possible to spy on Van Eck radiation to read what's on a monitor from a distance but the equipment required to do so is either expensive or complicated to build. It's also a non-trivial problem to tie what's on the screen at that moment (an analog signal) with what's being typed. I'm quite satisfied that the barriers to that my monitor and mouse emanations being compromised are sufficiently high to discourage all but the most determined hacker. Realistically, you can never make something 100% secure. All you can hope to do is to raise the barriers high enough to nudge them along to easier targets. Rest assured that there are many easier targets. I can see 2 completely unsecured WiFi networks from my house and I suspect this is constrained by the distance between houses more than anything.