Frankly, I'd wait. I have the same setup as you (8.1 and 64bit), plus a Surface Pro in the mix. There are still too many issues with sync. MANY people can't get it to work right.
I reverted to 2012 and won't go back until I see more happy news on the sync forum.
One of the other replies to your query makes sense to me. Their network seems to be struggling under the load from the new sync regime if nothing else. Apparently 2014 synced more information.
Wait ... even the first patch doesn't seem to be going over well ...