I have now made another CSS style for BazQux and it look really nice (to me at least). Reading fonts are bigger and anyone can easily change that. Check it out here:

http://userstyles.org/styles/90700/bazqux-reader-white

If using Chrome, Safari or Firefox, a userstyles addon is necessary to install this. I do not know about Internet Explorer (I am on a Mac).

I had this very problem. O solved it using a couple of lines of CSS. I have put it here:

http://userstyles.org/styles/89881/bazqux-reader

Enjoy!

@Marc: I haven't used used Opera 15 (waiting until everything settles down) but I do use Opera 12 from time to time. So the answer to your question is no, I've no idea whether per-site custom CSS will be removed, but I'd be very shocked if it was. Opera's great strength, to me, has always been its flexibility. If they take away the ability to customise it, what's left to distinguish it from Chome? Even Chrome allows Greasemonkey-style scripts...

Thanks, Vladimir. Font customization would be a very helpful addition.

@JohnK: That sounds like a very good work-around. Unfortunately this custom CSS option looks like to be removed in Opera 15, which is the browser I'm currently using. Do you happen to know if this is still possible in Opera 15?

For now, you could always change the font setting by using CSS. Some browsers allow per-site changes to CSS (Firefox, Opera, that I know of).

To change the message font and width of the message pane, for example, you would add this to your userContent.css file in Firefox (sample values included). Notice I've changed the font colour to a dark gray as well:

@-moz-document domain(bazqux.com) {
/* message body -- fonts, colours, article width */
.post .msgBody {
max-width: 625px !important;
color: #333333 !important;
font-family: "Source Sans Pro", Bitter, "Open Sans", sans-serif !important;
font-size: 15px !important;
line-height: 24px !important;
}
}

I have changed quite a lot of Bazqux' interface using the userContent.css file in Firefox:
https://dl.dropboxusercontent.com/u/13895942/Bazqux2.png

Don't forget to make max-width of the text customisable too. With ability to customise fonts one might want to make width of text (line length) to fit their preference too.

That would be great! Can't wait ... :)

I plan to customize fonts, font sizes and colors in future.