Not really any better than a regular rabbanut hechsher. Certain locations have been checked out by rabbanim who are not affiliated w/ the rabbanut and been deemed good. If you can give a specific case I can give you a better answer.
I have a rav who teaches people for smicha in issur v’heter I take my kashrus questions to – he told me in theory it’s supposed to be somewhere between stam rabbanut and mehadrin, but that he feels anyone who eats mehadrin shouldn’t trust it.