Is their source code auditable?
Would you trust them if their source code was auditable? Based on my experience, code security auditing relies on a certain level of trust. It is good practice when you don't trust the technical expertise of the company, not when you don't trust their intentions.
I don't see how doing thorough research suddenly makes blacklists and censorship "reasonable" after incessant pearl clutching and preaching how those services should be avoided.
Premium mixing. That's it. If you want to make a regular mixing, then use a software that will pick coins at random (i.e., will treat coins equally). But this particular service sells a product, and that is mixing with investors' money. Why would you want to do that and how you can verify you've received the product is something you should ask in their ANN thread. I'm not affiliated in any way other than advertising.
As a money transmitter, centralized custodial mixers are legally required to maintain records, respond to law enforcement requests, report transactions over $10,000, and file reports on any suspicious activity.
I'm pretty sure that doesn't apply on every single corner of the planet.