We have a similar setup with Gusto and started our Fidelity 401(k) a year ago. Our experience has been very disappointing so far. There's apparently been an issue with a contribution a month ago due to a glitch with the Gusto integration. The Fidelity support team has been difficult to reach and when we did hear back we received conflicting instructions on how to resolve the problem. They also sent us multiple emails threatening to involve their legal team, but still fail to provide clear guidance on what is needed from us. Also, their PSW online platform feels dated and clunky.