I've never worked with UML, but part of me wants to like it. Part of this is a reaction to (IMHO) an excess of "agile" methodology and a corresponding lack of

I've never worked with UML, but part of me wants to like it. Part of this is a reaction to (IMHO) an excess of "agile" methodology and a corresponding lack of forethought. The more intriguing part, however, is the idea of subdividing the problem using visual formalisms, and diving down into code to formalize the trickier bits. I wonder if there's a clear boundary beyond which visual formalisms are no longer effective? I'm reminded of visual proofs in mathematics, and their reputation for being unreliable and misleading. It would be cool if we could identify a subset of cases where visual formalisms were (nearly) as rigorous as lexicographic ones, but nevertheless more intuitive.