I really liked a lot of the songs. 10 is a huge undertaking, and not all are going to be memorable. I can name over half of them and really like them though: Shake Your Tail, Battle, Welcome to the Show, Shine Like Rainbows and Under Our Spell. That doesn't include the final battle song (once Sunset gets the mic) or Tricks Up My Sleeve, both of which I enjoy in the movie, but might not look up on Youtube any time. That leaves Awesome as I Want to Be and the other Rainboom song and whichever other one I've forgotten, so all in all, very quality.
Reusing old jokes? Always going to happen. It's a throwback to old memories. The one about 20% less awesome fit very well and made me smile. Other examples aren't coming to mind, but I do remember other throwbacks. I don't think they distracted from the movie.
The movie did indeed focus on Sunset Shimmer (and Twilight) but that's called leading with your best asset. A nice change from only ever focusing on Princess pone. And least we got someone new to outshine everypony. The two actually showed some good development and bonding over others expectations of them. I know that Sunset's villain-friend turn is the quickest in history, but lets put that aside. That's the first movies problem. Rainbow Rocks made excellent use of her in this new situation.
Regarding a few words on the others: Rainbow was almost an antagonist. She had the most scene time, but not for reasons I enjoyed. A further descend for her into near Diamond Tiara levels. Pinkie is still comic relief and unused for anything else. Rarity was barely used at all. These trends are problems that should be addressed, but they are characteristic of the show in general, not Rainbow Rocks. Fluttershy at least had some cute scenes and Applejack continues to be the ever perfect rock that grounds the ensemble.