My first mouse was faulty - it just looses communication with the cursor and needs to be replugged every few seconds. I had it replaced and the new mouse, initially, was the same. Then it settled and worked well for a few weeks. Now, the old problems are back and worse than before. I'm repeatedly replugging it just to use my computer.
I check these forums when I'm considering a new product, so I'd like to issue a warning to potentially purchasers. The Mac Mice site explains that 0.1% of their mice are faulty, but it seems to be rather higher... unless I'm unlucky enough to get two duds in a row from what must be a relatively small production line.