We've stuck to virtualenv and pip mainly for the reason that we've got plumbing that works and we'd rather be doing other things than finding new plumbing.

Very few issues arise from our choice of build tooling. Not enough to consider switching at the moment. I suspect I'll try pyenv next time I have a new dev maching to set up but only as it seems fairly painless to switch from virtualenv.

There's a lot of "shiny new toy syndrome" where people want to try the latest tool that is "allegedly" better but it's a pain in multiple other factors.

Pip works, virtualenv works. They might not be great tools, but they do the job.

I don't want to worry to much about my environment, that's why I'm skeptical about new tools. Because they might break when you least expect

Pretty much.

Virtualenv solves 90% of the problem, and it is not like you need to revisit your setup on a daily basis.

I would be more willing to spend time on my test setup than anything else, because that affects the development experience.