I'm sure it's too late now as I see the final has been released...
It appears the AMD64 version has issues playing H.264 videos. An informal thread in the users forum asking about who does and who does not have issues seems to show a pattern. The green blocks growing from the left side of the screen went away somewhere around 710b3 for i386 users, matching the change log notice of upgrading lmce to the latest version of xine. However, up through R1, the AMD64 version still has the green blocks making H.264 videos pretty much useless.
Another annoyance.. I upgraded from B3 to R1 (AMD64), and while the install found my previous install and I selected the option to keep /home and the settings, it wiped everything out. Video settings, TV settings, Myth, static IP settings (which I had to manually fix before any of my computers could get back on the internet), resolv.conf, my non-lmce server apps such as postfix and dns.. All gone. Some of this may be related to the fact that the first attempt at installation hung at "update-initramfs: ...." and I had to reboot and start again. After unplugging my external USB drive the second install went fine (other than wiping everything out). I was careful and selected the keep settings and /home option both times. I'm not sure if having the USB drive connected is what caused the install to hang, but on the second attempt without the drive the install went through nice and quick.