The only apps I had on Android were Kivy launcher, SL4A, AndroidScript, Bit Web Server and Tasker. Truth is I like to write scripts if there's some functionality I require that isn't already built in (my paranoia again) so I'm not really very qualified to comment on apps.

Firefox OS doesn't seem to have a developer mode and I believe if you want to write JavaScript that accesses device capabilities you have to get it signed so I'm sure that will bug me at some point.

I hope Mozilla will add a developer mode in a future iteration of Firefox OS, smartphones are pocketable computers and they have uses beyond what the manufacturers might have planned for them.