I have IntelliJ Ultimate, but I'd actually love if my license would also be good for PyCharm, RubyMine, etc.
Obviously, you can get much of the same functionality by installing all the relevant plugins in IntelliJ. But, the per-language IDEs are nice in that they are tailored for that specific language. Also, they have a lighter footprint, since the plugins for the other languages are not loaded. And I don't see disabled JRebel buttons, etc. when working on, say, a Python project :).
The extra niceties of language specific IDEs over IntelliJ is supposed to provide a reason for giving JetBrains more money to keep up the good work. Their tools are surprisingly cheap when you pay for your own license.
Obviously, you can get much of the same functionality by installing all the relevant plugins in IntelliJ. But, the per-language IDEs are nice in that they are tailored for that specific language. Also, they have a lighter footprint, since the plugins for the other languages are not loaded. And I don't see disabled JRebel buttons, etc. when working on, say, a Python project :).