What are some of the UX problems you're thinking of? Personally I've been pretty happy with it so far. (My main point of comparison is Sibelius, which I used until I went all-Linux three or four years ago.)
The one that's almost a show-stopper to me and I realized it only recently: if you insert notes (between existing notes), it won't move the existing notes to the right, but it will instead create this "long" bar with more notes than your time signature.
Really
I recommended this software to someone, and my first words were: “This is a powerful program, but it has got a steep learning curve. It feels like it was designed and written by a programmer who also plays music”
The answer from this person two weeks later: “You were totally right. Very frustrating.”