I hope iTunes 12 can fix the home sharing and AppleTV. It has been a mess, super slow and make impossible to watch anything from my computer. It's not the network because iTunes Store, Netflix and anything over the net works just fine.
hasnt been fixed it on my rMBP and itunes 12...
i click on a 40 mins episode and it already takes forever to even start, then it plays for like 10 mins just fine before the time has caught up with the current buffer and it appears the apple tv hasnt bothered to buffer more when all of the sudden it buffers like 30% in 2 seconds before it stops buffering once again. like u said netflix etc work just fine. it has gotten so annoying to keep checking if the file has been buffered enough all the time that i just use an hdmi cable to watch local content straight from the macbook at this point