Finder and Launchpad are both significantly faster for me. Quicklook works instantly for all types of files. It seems to be a good day for finder on my mid-2011 iMac with an SSD.
But...
Edit: Airplay Mirroring is now working, after tracing the issue back to 3rd party software. I knew it had to be 3rd party after realizing that it worked on my clean install of 10.9.3 but didn't on my working install. So I started installing the apps that screwed around with display drivers a bit and realized that the virtual display driver that is an optional install with Splashtop Streamer screws up AirPlay Mirroring, as does the app DisplayPad, which allows you to use your iPad as a wireless extra monitor. I do find it interesting that I had no problem with these apps and drivers coexisting with AirPlay Mirroring prior to 10.9.2 though. I'm just no longer sure who to blame for the problems. In any event, I'm glad I've found an acceptable fix in the meantime, though hopefully the developers and/or Apple will figure out a way to get these sort of features working in harmony with AirPlay Mirroring again.
And restarts are still hanging. After all of these months. That really shocks and disappoints me...