Overall, I like the feel of the site. I'm a minimalist myself, so I understand where you're coming from. I do have a few comments, though:
Background music: This is a pet peeve of mine, and I know there are others out there who don't like it. I appreciate the fact that the music can be turned off, and that the device is featured prominently, but I think the music should be off by default. If someone wants to listen to the background music while browsing your site, then they can turn it on.
Too little: Less may be more, but I think there comes a point where too little is too much. For me, this design just looks washed out. There is too little contrast between the white background and the light gray, and the odd colored-text highlight is just not doing it for me. Aesthetics aside, the lack of contrast between the text and the background makes the site less than comfortable to read. It's not unreadable, but it's not as comfortable as it could be.
Pixel font: I find the pixel font (used in the menu and other areas) very hard to read. It mixes upper and lower case, and distorts some letter shapes. I don't know if it's supposed to be cool or not, but I don't think it's a very good typeface.
Vertical space: The header area is way too big. The header graphic itself takes up almost half of my browser area (maximized at 1024 x 768) vertically, and when you factor in the navigation bars in the center, the content area itself starts two-thirds of the way down the page. To add insult to injury, certain pages have vertical scrollbars, which means I have to manipulate two scrollbars (the internal scrollbar and my browser scrollbar) to see the content. This is not good.
404: I'm not sure how I feel about simply having an image for a 404 page. Perhaps an image and some plain text? I think it would be more accessible that way, and easier to process even for those of us who don't have to worry about certain accessibility issues.
Copy: Check your copy thoroughly. I noticed a few awkward spots, like "these tutorials are provided to you by" (on the Tutorials page). You might want to have a third party give it a once over to catch glaring errors like that.
That might seem like a lot of criticism, but I think the site has a lot going for it as well. It is simple, and that is a good thing. It's also consistent across the board--even the forum fits in, which is a rarity. The things I mentioned here are just some things that I think are preventing the site from fully realizing its potential.
[Edit: Grammar 'n' stuff]
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Suho: www.liminality.org