I'm a novice comics reader and I too subscribed a few days ago to MU. I already read a lot and for the price it's a great service but yeah, the app is seriously lacking in many aspects, especially coming from comixology.
It crashes more than it should, it restarts randomly when you multitask from one app to the other, there are no manual or automatic bookmarks so when it does that you have to manually pick the page you were at. It's hard to follow a series, personally I add to the library the issue I have to read next from the last page of what I'm done reading and then go back to the library and delete the one I just finished. This way I only have what I need to read next in my library. It's not that slow but it's annoying, and you really don't keep a good track of what you have read so far.
Also, new releases much be checked manually, there's no "subscription" option anywhere. Oh and panel by panel reading in comixology is hundreds of times better. And there's no single-page landscape reading as well, which on iPad mini is a pretty annoying problem.
Still I would recommend it, I would have spent a fortune to read what I managed to do in just two days.