It may have only taken me 2 hours to beat the whole thing, but I can safely say this is probably one of my favorite games ever.
It's everything it promises to be - psychadelic, mind-bending, and hallucinogenic, while also being engaging, reasonably challenging and having a solid mechanical foundation and gameplay.
First of all, it does a great job of easing you into the game as it adds new mechanics. It starts out simple to let you learn and ramps up from there. There's really only ever 4 buttons to worry about, too: left and right, hook, and lance. The fact that it is so simple control-wise means it's that much easier to feel immersed in the game and not worry about what your hands are doing.
That's hardly what makes it great, though. Each level feels like a unique audio-visual experience. In order to complete level goals, you have to be constantly looking ahead down the "pipe". As you perform certain actions, the visuals AND audio react accordingly. The fact that you have to be watching in a certain way and processing what is happening visually, all while everything is changing and responding to what you are doing, is what makes this such a psychadelic, engaging experience.
If you're used to arcade-style games where the focus is on precise, responsive controls and clearly defined, easy-to-read game state, you might feel put off by the idea of this game at first. Everything is constantly moving and waving around and oscillating, which you would think would make it hard to keep track of what is happening. As far as I can tell, though, this is intentional and doesn't hurt your ability to start to gain mastery over the game. As the game state changes (for example, as you speed up), the way you need to visually process and respond to the game changes as well, and the visuals and audio respond to keep feeding you the information you need.
The "ending" is a huge treat; an audio-visual dessert which somehow manages to top the psychadelic experience of each of the levels.
Once you've played through the game, there's plenty of replayability playing through individual stages to get to the top of the leaderboards and competing with your friends or the general public, going for trophies, or even just enjoying the remix mode. However, it seems the friends leaderboard isn't functional (at least for me), so I was a little disappointed by that. Also, the leaderboards don't seem to let me scroll to the next page, so I can only ever see the top 20 or so scores in the world. Perhaps this will get fixed later.
Definitely get this game unless you are concerned about the overwhelming visuals causing diziness or something like that (it wasn't a problem for me and I get motion sickness pretty easily).