I have been interested in formal methods for some time. I have used formal methods to reason about some very specific sub-areas of a few projects I have been working on. I was never able to convince other team members to try the same let alone specify an entire domain with a formal method.
One method I have found particularly interesting is Alloy. I think that it may "scale" better as foundation for an entire project because it is conceptually and notationally very close to actual programming languages. Furthermore, the tools are quite solid so that the benefits of model verification are readily available.
I'd be very much interested to hear about any real-world experiences you folks might have had with using Alloy in your projects. Do you feel that it has helped you in designing a better domain model? Did find errors in your domain model during verification? Would you use it again?
Yes, I've used Alloy and it's cousins industrially. Alloy has been most helpful in convincing me that my models weren't wildly wrong---or rather, showing me where they were wrong and gave rise to silly results. Other more specific tools, like Song's Athena and Guttman and Ramsdell's CPSA have been more useful in their narrower domains. What more would you like to hear about?