The reason we chose this look and stuck with it through so long is that it appears to be rather pleasant and calm. In the past I would redesign the site every few months because I was sick of how it looked but having done it like it is now I was finally happy with it and most people that have spoken about it agree that the current look is neutral enough not to bore you quickly. And that's important with forums cause they are used a lot and having a design that isn't dominating is crucial IMO.