> And I'm pretty sure the reason portage is so extremely slow is because it is in Python (I've checked, it's not I/O-bound)

I was under the impression portage was "slow" (relative to other package management tools) due to the fact that it built everything from source (for which it uses make). Where is the Python bottleneck?

> In fact, give me a single big desktop software project made with a language that is not C or C++.

What constitutes "big"? There are a few large desktop projects that run on the JVM, for instance.