I'll share my experience this past January. Got to MK before it opened, but the lines to check bags coming from the buses were insanely long. At that point, we decided to divide an conquer. My DH stayed with the backpack making the line while my kids and I went through the no bags entrance. Our goal was to hit Space Mountain first, so we went straight to the area where everyone was being held off while they checked magic bands and allow the resort guests through. That meant that whether you were staying at a resort or not, you were let into the park. At the pathway to get to Tomorrowland was a complete mob scene, there was an insane amount of people trying to get through. It was so packed that the CMs decided to open the way for everyone, resort guests or not. When we got to Space Mountain the line was very long and we waited about 45 minutes for it. Got off the ride to meet my husband who had been in line for bag check for a WHOLE HOUR. So there, EMH was a complete waste of time for us. We eventually hopped to Epcot where I had made our FPs. Granted this was on Friday, January 4 and the Christmas crowds were still there. So it all depends on how packed the park with EMH is. Best of luck!