I was reading the "What makes or breaks a barleywine" thread and there was some discussion of the BU:GU ratio that Ray Daniels introduces in "Designing Great Beers".
Great book, totally worth it. But I'll add this.
Check out the information at www.beercolor.netfirms.com where they talk about something called the "Balance Value", which is one step further than the BU:GU ratio. It's a good read if you are scientifically-inclined or interested in brewing.
I won't bother paraphrasing the article. But I will say that I've added the following calculations to my brew spreadsheet and used it with good success on my recipe formulations. I've also added their listings of BV for the BJCP categories to a database and refer to that as my standard.
BV=0.8*BU / RTE
RTE = (0.82 X FG) + (0.18 X OG)
Guideline based on average BJCP values.