Only MK and Epcot have evening EMH; it used to be all four parks. They're two hours now, compared to three up until a couple of years ago. And when it comes to the MK, the regular hours tend to be short on EMH nights so instead of the late nights we used to get, it is just a normal length day with the onsite-guest-only restriction in the last two hours.
In Jan 2012, with crowd levels of 1 to 3 according to Touring Plans, evening EMH ran until 1am at the MK. In March 2011, with crowd levels 4 to 6, MK EMH ended at 3am. This year, EMH ended at midnight over 4th of July and 1am over Easter.
ETA: I think the cuts have been more obvious to those of us who like the late hours. There's still 4-5 morning EMH most weeks, and they're the same 1 hour they've always been, but there's less and less for night owls at WDW (pool hours are shorter than they used to be too).