As of early 2004, the only cordless optical mouse I would recommend is the Logitech MX 700. 800 dpi means nothing if the signal is updating at ~50 Hz (Microsoft ones are even worse, at ~30 Hz), thus the cursor jitters as you move it. The above-mentioned mouse updates at 120 Hz.
The downside is that it eats batteries like candies (part of the reason why the refresh rate is so low is to conserve power). Fortunately, it comes with two AA NiMH, and the receiver doubles as a charging station.
It is also, unfortunately, not left hand friendly.