The project I am leading at this point is a combination of c# and java. We use the reflection (or introspection) to make code generic. This saves project effort a big time.

You said :"...There's nothing that can be done with run-time introspection that cannot be done (better) by compile-time decision taking...". yes and no, some of the reflection code can be really smart, but when you done it at compile time, it ends up with ... something like a long life of if elsif.

The downside I suspect is performance. Still wait to be seen as the project is going. Nowadays you don't care whether it is slow, you care whether it is bearable.