I'll keep this brief and spoiler free since most probably have not seen the movie yet. Unlike strikers which sidelined the main cast in season 1 and 2, and vivid which basically almost changed the main cast entirely, Reflection retains the main cast from season 1 and 2 therefore it was an instant plus to me. The main cast has great chemistry and therefore is always a joy to watch them interact. Reflection's tone is similar to that of season 1, 2, and 3 (Strikers), not very lighthearted like that of vivid. Although not as well executed as As, the villains (well most of them)have believable motives which you can empathize with. The movie does end on a cliff hanger leaving many loose ends that will hopefully be tied up in the Nanoha: Detonation.

Overall, if you are a fan of season 1 and 2 or movie 1st and 2nd of the nanoha anime, you will most likely like Reflection.