Skeptically, I upgraded to Lion yesterday morning and frustrated to say, like many others, I'm at a loss for how awful it is. I've already spent an hour diagnosing a broken wireless config (losing internet connection every 20 mins -- fun!), but now... Here's the next issue: I'm running an iMac (purchased Dec. 2011) with a Magic Mouse, and I've already disabled the gesture options, but I'm having the weirdest issue with mouse behavior. It seems that whenever an application is tasked with needing a lot of internet bandwidth -- for example, uploading a large file in Transmit -- the mouse becomes INCREDIBLY sluggish and choppy. Precision of any kind becomes completely impossible, and as far as I'm concerned my machine is rendered basically unusable. I could keep complaining, but I'm hoping instead someone else has experienced the same issue and can relate. Even better, there's a solution to be found. Any help? UPDATE: Turns out this looks like an issue I hadn't even considered -- wireless interference. For whatever reason, Lion must have switched channels on the pairing of the Magic Mouse. Unpairing it was a good start, then restarting and resetting the PRM. Afterwards, if more issues persist (I'm still having some mild sluggishness), might have to go so far as changing the wireless channel designated on your router.