Very nice, that's not a thunderball obviously,but it works fully.
A iussue, Redstone didn't fixed the phone crashing when swithcing some apps to homescreen tapping back key (I'm sure that's a video overflow memory, too low ram)
On 520 I got always the same freeze: always exiting Messages tapping back. So I became used holding back for popping up task manager, or using directly Home key.
No other iussues, exept the low ram obvious (unable using flawless Messages, Whatsapp and Edge togheter, e.g.)