Hats off to Dave Shea for his redesign of Mozilla.org (publicly released beta). Nice, clean design and structured markup. It's a great contribution to the project.
Also of interest are Dave's notes on the response of the beta, and what's left to tackle.
In general (and as Dave mentioned), thick skin is needed when designing a popular site (like Mozilla.org). Validation, accessibility, design choices, browser quirks -- just a few of the hurdles to leap over when redesigning any site -- but are then magnified ten fold when dealing with something larger than your average personal site or weblog.
The reality? Getting everything 100% "correct" is hard stuff.
Feedback is important and necessary, and trying to break a design -- turn it on its head and shake out the bugs -- can be invaluable. But what's important is this: when all is said and done, any attempt in making gains in validation, accessibility, markup structure, etc. make the web site better than it was. And if you fancy yourself a web designer, your first gesture should be a tip of the (Red Sox) cap to anyone who dares.