Make the installation easier?
As a researcher in software ecosystems, I recently encountered performance issues on (quite) large graphs with NetworkX. I then considered using graph-tool. However, as a Fedora user, I had great difficulty in finding an easy solution to install graph-tool. I didn't find any package targeting Fedora/CentOS, I didn't manage to turn the provided .deb into a valid .rpm, and I didn't want to spend too much time compiling graph-tool and its dependencies.
I then moved on to igraph and its Python binding which were fine for my purposes, but I felt that I should give it a try with graph-tool. I think you should consider making the installation easier for (some) Linux users. The first solution is to provide packages targeting Fedora/CentOS, which is quite a major distribution nowadays. The second solution is to provide wheels for (major) architectures on PyPI, which can be quite a difficult (and annoying) task. The third one, which could be easier for you, is to consider Conda and, more specifically, the open-source Conda-Forge (see https://conda-forge.github.io) that provides a very simple mechanism for developers to have their package automatically build against the three major operating systems.
Btw, thanks for your job. I hadn't a chance yet to test graph-tool, but I enjoyed reading the documentation and I hope I'll be able to perform some research with it (I've to admit I really don't like the API of igraph's python binding nor its documentation).