That's also what I was thinking but I'm a little wary of using something in production which I don't use in day by day development and I run tests against it only a few times. It seems a recipe for letting bugs slip into deploys.

By the way, I googled a little and removing simplecov shaved a couple of minutes out of the rake spec times. Still too slow and very inconvenient, even if I can still use simplecov with MRI thanks to conditionals like if RUBY_ENGINE == "ruby" ... end