The recent Newgrounds survey had the following question at the end:
If you would like to provide any feedback or suggestions for Newgrounds, please do so here:

This is what I wrote (edited into bulletins):

1. Treat the music portal seriously, not just as a source of free music for Flash authors - we have some amazing artists there, they deserve it.

2. Give users EXPERIENCE POINTS for voting on music or art submissions, just like they get for voting on Flash submissions. That may encourage voting on new submissions (how come 200 people vote for each new crappy flash, but new music submissions are lucky to get a few votes?).

3. Make the experience points system for each portal separate - someone who has a highly-weighed vote because he votes a lot on Flash may not know anything about music, so his vote should not be weighed more until he votes on a lot of music.

4. Make a "judgment period" for the Music Portal (that might also induce more people to vote).

5. MAKE A YOUTUBE-LIKE OR DEVIANTART-LIKE SUBSCRIPTIONS SYSTEM!!! PLEASE!!! THIS IS THE MOST IMPORTANT THING, all the other websites have it. RSS is okay, but really limiting because you can't customize it. I'd like to be able to, for example, subscribe to USER-A's news and music, but not his flashes, USER-B's art, but not his music, etc. and have a record of everything that I've subscribed to, including a way to see whether I've watched an item yet or not (regular text if page has been visited, bold text otherwise).

6. Have an at least somewhat-customized ad system for the Flash portal, for example by allowing a submitting user to pick a keyword that best describes his submission, which will then make correspondingly-themed ads show up, instead of the same ads for the whole website.

7. Allow posts I made on other people's news items to be accessed from the userpage (like reviews and forum posts are).

8. Also, I'm sure you're working on this, but allow "favourite art" and "art reviews" to be accessed from the userpage.