I am interested in transitioning to the open stack. I would love your feedback on Ruby vs. Python vs. PHP vs [X].
All of the languages mentioned above have pretty good ecosystems around them. I think Ruby's is the strongest at the moment, but if you're more of a python guy no harm in that :P.
Honestly I learn as much as I can, and as such have done at least a little bit of dev work in all of the above languages plus some :P. Never hurts, and you'll be able to make a much more informed decision yourself afterwards.
About a year ago I started working with Ruby on Rails for all my side work and hobby projects. It really is an awesome mind shift from .NET.
So I guess my vote would be take a look at Ruby on Rails!