I've ran local dev sites on 7.3 and everything I tested worked, but I didn't test the important stuff (sales, etc.).
I was testing something else and my default dev stack is 7.3.
My production s2 sites are still on earlier versions because another plugin I use hasn't been updated yet so I don't have production testing.
I'd be very surprised if s2 had any code encrypted by ioncube or any alternative because they've always seemed very open to sharing all the source code.
The source is even on GitHub.
I haven't read it all, though.
@clavaque Are there any PHP encryption shenanigans?
As a programmer, one of the reasons I hate PHP is the existence of stuff like ioncube. That and they are slowly turning the language into antiquated Java rather than EcmaScript, Python, or Ruby.