Initial reports are flowing in, and I can confirm, that Panasonic AVCHD from their Professional/Prosumer video cameras no longer plays back with an image in 10.2 (image is black). Anecdotal evidence indicates GH-series stills cameras are fine, and I'm having no trouble with AVCHD from either Canon stills or C100s. Video from AF100s aren't working however.
Creating Optimized and Proxy media only produces ProRes with black footage, though oddly, running the original media through compressor works - however it is not feasible for complex projects already in progress.
I'm sure it'll get remedied, hopefully quickly enough to not scare us all into adobe's arms, but if you use such a thing, hold off for now. It's too bad, the promises of 10.2 UI speed-ups aren't overstated making and already fast workflow that much faster.