I think that I might wait for others feedback on this update before I install.
I have the same question as ejmccartin - I am wondering if they fixed the contact sync. I get tired of fixing all my contacts once the sync chews them up a bit.
0.5.12 fixed the contact sync issues for me. From what I am told 0.5.13 is related to a calendar sync issue affecting recurring events. I'm not sure about that, but I am sure that my contact sync is working just fine.