I have been a web developer for nearly 10 years, and this site has been the biggest help in my career. Educated and experienced devs from around the world converge here, and that's what makes it so valuable. The popularity is based on the content, not so much the look.
That being said, if you were my client and I was hired for consulting, I would recommend a professionally designed logo. Professional logos go a long way especially when it comes to choosing a color scheme for sections of a website and a company identity.
This is a forum, and a forum is a forum is a forum. So, I'd also say to maintain the forum/content credibility by not changing too much of the layout. Forums are already good at what they do.
I'm sure you know plenty of designers, but if you'd like I am in contact with a top level designer that wouldn't disappoint.
Definitely no harm in sprucing the site up a bit and doing a refresh of the drab look. I bet a few new webmasters go to other forums because they look better and miss out on a great resource and the forum misses out on new contributing members.
Brett did a crowdsource contest for the PubCon logo and those who participated came up with some excellent designs. Perhaps something like that could be done for WW, too. Throw it out there and let the members vote on which one they like best.