For me the stand out was the music, I preferred it to Echoes and thought it was nearly as amazing as Prime 1 (one of the best ever). The art direction was very good, the FPS controls were great and much better than dual analogue which has always been a shitty retarded control system anyway, and they gameplay was mostly good.
The other motion controls, they were nice first time, but annoying for most of the game. The level design was decent, but sometimes poor, and not a patch on Prime 1. The puzzles were mostly too easy, to the extent they weren't really puzzles, and when they were harder, like the Energy Cell in Bryyo's crane, they were so bizarre you weren't ready for them. Not difficult, just incongruous to most of the game. The boss battles were okay/good, but not as great or satisfying as Prime 1.
The biggest problem I had with the game is Retro tried to do too much. The contents of the game were spread too thin. I'd have rather had less abilities that were more useful and fleshed out. A longer game may have helped, but I'd had enough by the end.
Overall, I enjoyed it, in a 8/10 - 8.5/10 way.
Not as good as Prime 1, which is one of the greatest games ever made imo, and easily the best game from a first person point of view, ever, but still very good.