New version 6.3.13 is released:

http://boinc.berkeley.edu/dl/boinc_6.3.13_windows_x86_64.exe
http://boinc.berkeley.edu/dl/boinc_6.3.13_windows_intelx86.exe

Anyone know what specific changes were made to this release?

Yes, here are some.

6.3.12
- client: attempt to fix CPU sched bug in the presence of GPUs
(if there was an idle GPU, it would run unboundedly many CPU jobs)
- client/manager: show # CPUs and coprocessors in task display

6.3.13
- client: don't lower priority of apps that use >0 coprocessors and <1 CPU.
Otherwise they don't run efficiently.

-prepare for "don't run while playing game" feature

-client: add "exclusive app" feature. If you put
<exclusive_app>foo.exe</exclusive_app>
in your cc_config.xml, BOINC will suspend computing
whenever foo.exe is running (e.g., a game).

I suppose this would be useful when gaming, although it looks like the option suspends all boinc computing, not just the GPU. I have not tested as 6.3.13 gave me other problems and I regressed back to 6.3.10.

- scheduler: add <no_vista_sandbox> option.
If set, don't send work to sandboxed Vista clients
(e.g., because of CUDA issue)

There were many other but these are the most relevant.

The next release will have
- client: fix bugs in coprocessor scheduling;
add new <coproc_debug> log flag