I don't know about "very well," but I'd give this site a C or D for functionality and an A or B overall.

Let me put it another way -- this site works well enough for me to visit it just about every working day. I'm happy to do my part, occasionally replying when I have an answer, doing a little moderating and so forth. Sure, there are some quirks, but that's OK -- I'm quirky myself, so that fits.

The validator is useful when it points out major errors, and I try to use border="1" instead of border=1, for example, but if a page isn't perfect, that's not the end of the world.