The best (well, worst, really) part is when it ends in a state where the parts are almost right, but not quite. The result is, quote one of my coworkers, "We ended up with the architecture that is so flexible that we can't change a single bloody thing in it! What the hell!" The whole is flexible, but this flexibility is pointless: you can make the parts behave differently, but there is only one behaviour that is actually useful; you can combine things together differently, but there are at most two combinations that do things in a useful way; etc.