With Borderless/Multi-Currency it's even cooler, since it grants you local banking details in many different locales, so someone can pay you via ACH, FedWire, SEPA, EFT, etc and have that value reflected in your account almost immediately (depending on the transfer method) and (depending on the transfer method) without charge.
Isn't this convenience at the cost of trusting a third party, I.e. Transferwise, with your money? They can unilaterally hold, delay, or stop you from using your money.
Yes, that is true, however Wise is a heavily regulated entity (in the sense that they are regulated simultaneously by a number of global regulators). Broadly speaking they would have to have a very good reason - a legal one - to preclude you from accessing your money. The flip side is you have a legal pathway to recovering your value in the unlikely situation you describe. Pros and cons.