Make it a gaming-grade mouse and I'm in.
Capacitors may suck to have to recharge; sure, you have to put the mouse on its dock at the end of the day- but you do that with a battery-powered mouse anyways!
With a capacitor, 3 minutes gets you, say, 6 hours of use.
With rechargeable batteries, 3 minutes gets you 2 minutes of use (better mice unfortunately use propietary batteries).
Plus, you don't have to buy replacement packs when those rechargeable batteries die, and the mouse pays for itself if you're talking alkaline batteries.
Even if you're too lazy or forget to charge the mouse 3 minutes is about the time it takes for you to put the mouse on the cradle, hit the power switch, and by the time your desktop is useable so is your mouse.
This is a beautiful idea.