Having to work on poorly written s/w, having to integrate it into my projects, no, I would avoid it at all costs. It's going to be a hell of a mess to maintain and upgrade, and probably won't perform as good as a project that was designed from the ground up. There is a cost to designing everything yourself though, which is that development may take longer than expected, but this is OK with me and my employer, so I take my time. And the quality of the final design more than makes up for it.