This offer seems to be better then nothing ANDsth i have been waiting for

That means we can choose between two ways :

Stay on Scrypt and possibly loose our contracts within the next days or weeks
Switch to SHA with all its consequences

Yes, the conversion is very "expensive"

Are SHA payouts stable ?

I tend to switch, but the ratio should be more like scrypt 1:5 sha or at least more than just 1:1...