That said, I've been told that UHC's core language uses the ideas from Strict Core, and they have/had a student at Utretch (Tom Lokhorst) who was working on implementing optimisations like arity raising and deep unboxing for the language.
Many/most implementations of ML-ish languages use a similar approach. E.g. SML/NJ's Flint internal language is fairly similar to Strict Core (except for the lack of memoization of zero-arg functions, since that's not very often useful in the context of a strict language like SML) and uses the same kind of wrapper+inlinling to perform most of its optimizations. Note that in my experience working on SML/NJ's optimizer (using wrapper+inlining), such an approach to code transformation doesn't care about types at all, and indeed most/all of what tacc-hs09.pdf presents is mostly unrelated to whether the language is typed: e.g. the uncurrying of the zipWith higher-order argument is performed by the inliner (when inlining the various wrappers) without paying any attention to types. So types do not enable the optimization of higher-order functions: it's the wrapper+inlining strategy that enables it. Admittedly, the use of a statically typed intermediate language makes it easier to catch bugs in such optimization phases. Stefan