This is not so. You do not have to write down all the details of the complete software stack as build systems can be abstracted away (e.g. `gnu-build-system` provides the GCC toolchain, binutils, make, etc). Only immediate first-level dependencies are declared.

And in many cases you don't have to do even that because you can generate package expressions from upstream information using `guix import`. There are importers for CRAN, bioconductor, pypi, hackage, CPAN, and others.

> The user can install the version combination that you packaged, but can they easily try their own? Can they easily try to build with a different compiler/compiler version/set of compiler flags/dependency version/etc.?

Yes! We use Guix for multiple clusters at a research institute and of course users must be able to create package variants, with different configure flags or compiler versions. This use-case is covered very well by Guix.