Installing Rails on a Mac is largely trivial. It's literally 5 shell-commands, depending on the current level of breakage of rubygems (but that's a different story). Write a tutorial in your blog if you really feel this is hard for newbies.
The hard part is installing the exact same Rails on multiple Macs and deploying the exact same Rails to production servers that are not Macs. And when I say "Rails" then I mean the entire dependency chain which reaches far beyond Rails and Mysql. The hard part is having controlled service startup/shutdown scripts that work locally and across any number of servers in your production deployment. The hard part is configuration management and safely toggling dev/production/staging modes across all involved services. There's lots of hard parts; bootstrapping a vanilla rails is not one of them.
In fact: Naive bootstrapping can be harmful, just like the still virulent code-generator brain-rot in rails itself.
I make a living managing these things and have evolved multiple approaches ranging from chef/puppet, over canonical git-repositories that work cross-platform, to VMs. There is no one-size-fits-all once your stack outgrows Rails+MySQL, and it always outgrows that.
If you wanted to solve the real problems surrounding all this then a single-platform bootstrapper is nowhere near cutting anything.
For that you'd have to start writing a better chef/puppet, which are indeed more than ripe to be superseded. But this is far beyond the scope of a kickstarter project and I hope Yehuda will rather keep his focus on Ember...