I upgraded my camera today to the latest firmware.
Upgrade was smooth, the firmware uploaded and installed, the camera restarted and my entire configuration was retained. I went through everything and all of my settings were preserved, I didn't have to tweak or change a thing.
I haven't noticed any major changes, though the entire live view page seems to scale when you change streams to match the resolution of the image. I can't remember if it did that in the previous version, as I always look at the 1280x720 stream on my desktop.
Overall the upgrade was smooth, simple and glitch free and the camera seems to be performing as well as it was before the upgrade. I've read the release notes and while the changes are extensive, I'm unlikely use many of them because I don't anything that fancy with the camera. If you're hesitant to upgrade, don't be, it appears to be a very stable release.