It was the first time he'd used TLA+ (or TLA) at all, and it took a bit of experimenting to get used to it, but he soon generated a solid logical model and exposed a number of fringe flaws in the original proposed solution.
From TLA+ model to completed Java application took very little time at all, the logic was all there already, it just needed fleshed out in the language. It was also easy to split the work out amongst multiple programmers. He's argued that the total time, including learning TLA+, took less time than writing the application from scratch in Java and discovering the bugs as they went along.
About the only thing he disliked with it was that almost all (if not all) the tooling around it require Eclipse, and he hates that IDE with an almost unholy passion :D