For morning EMH at Epcot, the following attractions are open:
Mission: SPACE
Spaceship Earth
Test Track
Universe of Energy
For evening EMH, the following attractions are available:
El Rio del Tiempo (Mexico)
Honey, I Shrunk the Audience
Journey Into Imagination With Figment
Maelstrom (Norway)
Mission: SPACE
Spaceship Earth
Test Track
Universe of Energy
So ... whether EMH will be worth it for you will depend largely on how important these attractions are on your plan and whether or not you can work them into your normal day at Epcot. Nights are particularly lovely at Epcot -- the pavilion lighting is really cool, and you can normally catch a nice breeze off the lagoon. On nights when Epcot closes at 9pm, EMH does indeed go until 12mn, unless the park is emptying out quickly, in which case it may close earlier. But EMH evenings are scheduled to run from 9pm-12mn.