GTK# could use some serious love, as much as I enjoy Vala I would much prefer to be able to use Npgsql for database access than deal with the crapshoot that is libgda. Unfortunately after the GTK3 transition it seems nobody has really felt like maintaining GTK# much, meanwhile plain old C and Vala have been getting all the cool stuff (GTK composite templates, in particular).
GNU Autotools now has vala integration, just specifying .vala files in your source list will have automake run valac to generate the C files, which will then be compiled by GCC automatically. Going one further, the C files get packaged into your distribution tarballs so users don't need valac installed to compile your application.
The usual M4 headaches with autotools apply, but as long as you don't have some crazy build (just compiling libraries/binaries, linking with libraries, use pkg-config) it's not too bad.
As far as testing, GLib.Test [0] is part of the standard library. Since vala compiles to C at the end of the day there's no easy way to test other than just building a test runner, but it's not too bad to work with.
GNOME Builder is finally getting support for Vala in GNOME 3.20, it's still young but hopefully we'll have a first class IDE soon. Still, Builder has a long way to go before it even catches up with MonoDevelop, but progress is good, right?
