I'd recommend to untick "allow reddit to show me custom styles" in reddit preferences or else you may have a few glitches since subreddit styles can get pretty wild. I did very little to add compatibility with subreddit styles, partly to keep the code smaller and also because I can't be bothered.

I'd also recommend to disable RES night mode and other RES style tweaks for best color/style compatibility if you notice any inconsistencies.

Updates:
12/3 - Since this theme to be used more often by everyone else, thought I'd focus more on making it more thematically consistent.
11/30 - /r/all is now filterable so updated its look and colored time of post submission.
11/26 - A few small changes for RES. I don't use it anymore so I can't guarantee that it'll stay RES friendly if their code should change.
11/23 - I brightened up the gray theme a bit so the text is more discernable along with various other minor improvements.
11/20 Couple things: The recent owner transition caused corrupted styles. Also reddit updated its CSS. I've fixed it for the most part but at the moment since I'm maintaining basically 6 reddit userstyles, I think I may have bitten more than I can chew sometimes.
- Long time, no update. Just made a few small color and margin changes that I think most people would like.
- Update for side tables so they don't overflow. Also a couple small changes.
- A quick fix for the search bar. The magnifying glass icon is invisible but I'll fix it later.
- Blockquote color fix for black theme.
- "Improved" the gray theme some. Hope you guys like it. Though I'm careful to do too much because I'd rather keep code and theme to a minimum.

Thanks to:

Mardiweb - Brick background (http://www.mardiweb.com/web/).
~start-static - Cloud background (http://start-static.deviantart.com/)
subtlepatterns.com - Dark Denim & Light Cloth (http://subtlepatterns.com/)
fullyillustrated.com - Space Ships (http://www.fullyillustrated.com/)

Want a dark scrollbar for Firefox? http://freestyler.ws/style/125814/firefox-black-scrollbar