Yup Rubymotion isn't interpreted, it's compiled file by file to LLVM bytecode, this negatively effects development speed but it means it runs (roughly) as fast as pure obj-c (or so they claim on the rubymotion site).
We're using it at the moment to develop an app, it's great at keeping code DRY, debuggability on device kinda sucks atm though.
Given how RubyMotion works (not an interpreter unlike regular Ruby), if the app is slow (I didn't test!) then it's very likely not related to RubyMotion.
Your other comment in the same thread does not mention you using Cabify at all -- it's a general slant against the company for using "unproven technology".
And your account was created one hour ago, just to deliver these two negative comments here.