WordPress 35 Administration Panel Slowness

Has anyone else experienced some slowing down in the administration panel since upgrading to WordPress 3.5? The load times on my sites don't seem to have changed at all insofar as visitors and front-end users are concerned, but things in the back end seem to have slowed down (sometimes drastically). To make things even more fun, it doesn't seem to be due to any particular plugin or theme, as I've experienced slowdown across a number of my sites and they're using almost completely different sets of plugins and themes.

I also don't believe it's my host, as I've chatted with a couple technicians from Rackspace and they aren't experiencing any issues with their servers. Further, there's the localization of the issues (i.e., they occur only in the control panel), which makes me think there's a problem with WordPress or some sort of conflict between the current version of WordPress and something else (most of the sites on which I've seen the slowdown are running under Rackspace Cloud Sites, so it's a pretty standard LAMP setup).

On a few sites, the slowness has been drastic enough to hit the thirty-second execution limit I currently have set. However, the slowness isn't consistent. Sometimes it hits the execution limit, but most times it does not. Mostly it's just an annoyance, but one I'd rather find some way to address than wait for it to 'solve' itself through updates.