I've had my Magic Mouse for about two weeks with a MacBook Pro 13", and I'm starting to notice quite a latency in the movement.

It gets really bad whenever any performance heavy operation is going on, that creates almost a half a second latency. This happens even for small things, like when a web page is being rendered, sometimes even while nothing is happening.

At first I thought batteries might've caused this, even though it was at 50%, so I changed them for new ones, which (subjectively) helped for about two hours, but it's still really laggy.

I also tried using the mouse on different surfaces, again it seems to work a little better on the table than on my mouse pad, but it's a little laggy everywhere.

Is this behavior normal for the Magic Mouse?

edit: I've been using my Macbook with 24" LCD at 1920×1280 resolution. When I plugged out the monitor, it seems that the mouse runs much more smoothly, even when I run applications like Photoshop.

Could the external monitor be causing such performance lag? But on the other hand, when I use it with USB mouse Logitech G5 there is no lag, not even on the 24" …