To me it's fine as long as it functions, and makes everyone's life easier. I'm not saying you should use anything, as it still needs to function and be simple. If vBulletin is that, then I say go for it. I'm all for optimization, since I've written my site by hand in notepad2 and have valid CSS and XHTML (not considering the javascript crap that my hosting company puts in), but I believe functionality and simplicity should come first.