I absolutely agree on the virtualisation front, and I'm a steadfast Mac user. Dev systems should be close to production/staging to avoid weird bugs. I really really don't want to spend my time dealing with whatever version of Erlang I can get on my Mac when I could just apt-get it. Case insensitivity is also an issue when using Python with the Cookie library, and with the eventlet library (and that's just off the top of my head).

Added advantage of using virtualisation is I can easily trash and rebuild my dev environment whenever I need to.