Pay close attention to the documentation; the script environment doesn’t do what you think it does, and so you’ll be very grouchy.
I want to love Coda a lot; as I mentioned in my review of Komodo IDE, I mention as one of its downsides it’s so very not-native. Coda is extremely, wonderfully, beautifully native. So there’s that.
But it’s ultimately an app for cranking out WordPress plugins, not doing serious work. If you want to build serious, production web applications – and especially in something other than PHP – look elsewhere.