lol. That's messing with textures and shit that I don't understand... I think it's cool, but people have put lots of effort into making the game pretty cool as it is. I think that you're going downhill from modifying the game by one or two points. Sorta like having an MMORPG with a million add-ons to look like you're playing a totally different game. No! I don't have a problem with WoWers!
I see where you're coming from, but I have to disagree.
Audiosurf is a great game, and it would be fine if there was nothing else to it, but Dylan has gone to EXTRA work to encourage add-ons.
It would actually be "going downhill" as you put it to ignore this extra effort and NOT create add-ons.
Nothing is forcing you to use them, but that they're there gives people like me an extra dimension to the game.
I'm REALLY bad at Audiosurf, I play entirely for fun. I also get a lot of enjoyment making add-ons for it though, which is what has kept me interested in it. It's also why I'd like to see an update to some of the add-on stuff, but I understand it isn't a priority.

In short, different people enjoy different aspects of the game. Dylan has created a small subculture (including myself, ViRUS, h3x and a heap of others) by creating the add-on interface. It's only a good thing.