I love Tup, and have used it in production builds. It is the optimal solution for the problem that it solves, viz, a deterministic file-based build describable with static rules. To start using it, you probably have to "clean up" your existing build.

I don't use it anymore, for several reasons. One is that it would be too off-the-wall for my current work environment. The deeper reason is that it demands a very static view of the world. What I really want is not fast incremental builds, but a live programming environment. We're building custom tooling for that (using tsserver), and it's been very interesting. It's challenging, but one tradeoff is that you don't really care how long a build takes, incremental or otherwise.