I feel like this was the best one in the series, because they had time to iterate on a gameplay concept they'd done before (pong-like) while bringing in concepts from games that were completely different (bonus beats, more health levels (extra, meta, giga, etc)). The music also felt like it could actually be felt in the patterns throughout, as opposed to infrequently and only at certain health levels.
This feels insane to say, given how down I was on the entire series, but I feel like they could've kept making these games, instead of only continuing runner as a disparate sub-series (in a genre that's already pretty well-established). Their second stab at a pong variation turned out way better than the first, maybe their second attempt at any other other genres in the series also could've gone better.