My mouse cursor does often jump to a random part of the screen. When running InDesign, the cursor moving off-screen causes the whole documant to scroll to a blank part of the Pasteboad, so I loose my cursor position, and sometimes an object that was selected at the same time disappears off-Pasteboard.
For normal typing, the text cursor stops moving as I continue typing, so I lose text if I am not looking at the screen at the time. When the cursor stops, the contents of the window (at least I think it is the contents of the window rather than the window itself) moves slightly to the right and back again, then when the cursor re-appears it moves slightly again. This happens in all softwares: InDesign, Word, Safari web pages and (I think) in TextEdit. About every 30 minutes or so, sometimes longer. When I intalled M. Lion it was by the erase the HD and install method.
The mouse problem is not correllated with the charge level of its battery.
I will try again to use my Kingston optical mouse (it seems to use a generic Apple software). (I lacks many features of course.)
I also use the Trackpad in parallel to the magic mouse and it never gives any trouble like the above, although when I barely touch it it sometimes clears the Desktop (as with the three fingered spread gesture), or displays all windows unstacked (as with the three fingered upward gesture), or it zooms the screen.