We are not night owls, so they aren't ideal for us (we get too tired!), but if you are, they can be great.
We have only done them once in each park, when we were staying at Boardwalk. MK was great. Short lines everywhere, especially by the second hour.
But Epcot is just so spread out, and the high demand attractions are so far apart, it's so much more walking than MK. If you do it, and want to hit all the headliners, I'd strategically plan your order. For example, if you are staying at an Epcot resort, do Soarin', Guardians (if you can get a VQ), Test Track, then Frozen, then Remy. It's still a ton of walking, and if any have a residual queue, you may not fit them all in in 2 hours.