I like the companion dialogue, but there is a lot of repetition, and it does get annoying. It's also kind of puzzling, because there's quite a lot of recorded dialogue, since I'm getting new lines for different areas, neat little chats between my companion and Leah, when she's along. There's really no need to repeat stuff.
The difficulty thing is interesting. The design decision is clearly that the real challenge doesn't start until higher skill levels, which is very much catering to the hardcore and those with a lot of time to play. I totally get why Walker and many others find it annoying. I think it's also down to the class you play, however, since these games often seem to make melee pretty much easy mode for the first playthrough, since they're so tough. I'm finding my Demon Hunter is throwing me challenges now and again even in Act I, and I really do need to make good use of my skills to keep fighting even in normal fights.