Our experience wasn't great. I attributed it to a difference between dh and me in ability to recognize and write down our feelings (I'm good at it, he is not). I thought it could've been valuable, but since it was not meaningful to dh, it became very difficult and frustrating for me. I don't think ME is BAD, just perhaps not for everyone. I didn't feel like we had to cry into each other's shoulders, or anything. I thought it did present a good form of communication, but not everyone will take to it as quickly as others. I think that a large number of people would need extensive practice and one on one instruction/training/counseling to learn how to recognize their feelings and express them in the way that ME wants you to. To be clear, I think that their form of communication is sound. But if one of you is not quick about learning their method, you are not going to get anything out of it.
Then there are the people who already communicate really well, and don't need the dialogue method. I can see how it might be the wrong focus as well. ME definitely comes at you from the perspective of "you are missing a tool to have a good marriage, come here and we'll give it to you." I'm sure there are plenty of people who don't need that tool, but who could still benefit from a marriage retreat.
On to the liturgical abuses. Depending on what you mean by "receiving communion together" I don't know how wrong it is. But here's the thing. No one is going to make you and your spouse do anything, so if you don't want to receive communion together, then don't. I don't remember exactly what dh and I did at the Mass, but I'm pretty sure we went into the experience knowing that there might be some liturgical problems, and that we would just do what we knew to be right. No big deal. I wouldn't throw out an entire weekend of good instruction on communication, simply because the Mass at the end might be a little goofy or have some liturgical abuses. That would be like throwing the baby out with the bathwater.
Same with the after-sessions. If they're not your style, and if the group thing doesn't work for you (which it wouldn't with us), then don't do them. I looked at the ME experience as a learning process, which happened to have some fluff along side it. If you can benefit from the main stuff, just throw away the fluff. Of course, if the whole idea of ME doesn't work for you, then that's another story.