Andrew Sullivan is alarmed about McChrystal's possible connection to detainee abuse. http://andrewsullivan.theatlantic.com/the_daily_dish/2009/05/stanley-mcchrystal-a-history-of-torture.html
I'd like to find out more, but I'm generally in favor of firing unsuccessful generals. One of the worst attributes of the Bush era was an extreme reluctance to fire anyone over failures, although any hint of "disloyalty" resulted in a swift sacking.
In contrast Gates (and Obama, it seems) have demonstrated a commendable willingness to demand results and let go leaders who fail to achieve them. Serious failures of judgement, such as that exhibited by Caldera with the Air Force One flyover, have also been cause for termination.
It's unfortunate for those involved, of course, who have in many cases served long and admirably. And there should be no shame in being relieved under those circumstances. It's not a scandal. Not everyone is suited for every job. But at these very high levels, with so many lives at stake there can be no shirking of the command responsibility to demand results. Generals, in particular, should understand that nothing less than success is acceptable and that the commander-in-chief will keep trying until he finds the right man or woman for the job.
I can't help but think that Obama is, here, also following the lead of his hero Lincoln. He's searching for his Grant. Only time will tell in McChrystal is Grant or just another Pope, Burnside, Hooker or McClellan.