It also remembers the file name when writing those frames, which is nice. And I notice when I add a morph it doesn't default it to spline, which always caused it to screw up all previous frames. The new morph takes effect on the frame it was created in.

I'm not noticing a speed improvement though. The one render (Superfly) I did as a direct comparison was actually slower in P13 than P12. 1150 vs 850 seconds. Ran it multiple times in both versions to verify it wasn't a setup issue. I also noticed some changes in the result, maybe more glossiness now in some places, a little less shine in hair. I expected to see some things change due to the Cycles update though, nothing really substantial here.