I'd be wary of this until it's a few years old.

I used to have an Amex High Yield Savings account, and it was a complete PITA to administer. After multiple mishaps, I closed the account. Even after shutting it down, it continues to appear in my online account and multiple calls to Customer Service and Tech Support result in me being told that there's no way for their IT to stop displaying the account.

I have no doubt that it's possible for Amex to invest in building and deploying the correct infrastructure to run checking accounts (and manage the required regulatory compliance) but their track record for their non-Charge/Credit Card Products is pretty bad. I'm very skeptical that they've done so here.