Generally, if Stripe etc claimed the money was on the way, Mercury's app already saw the funds and made them available by the time I received the Stripe email. Underneath the hood its Evolve Bank and Trust (or at least my bank account was).. Mercury is merely the smart software layer on top of the actual bank account they open on your behalf behind the scenes.
* The only slight negative is that they did terminate my account last week - they immediately suspended all in/out transactions with no warning, and said they'd either wire or cut me a check to get my balance out in a few weeks. I think it's because I asked their support a question about bringing one of our other much larger businesses across and so asked some ACH related questions which probably spooked them due to lack of understanding.
I'd use them again quite happily in other businesses though.. just be mindful if they do shut you down you might find yourself unbanked for a period of time... and the wire to get your funds out if they suspend you requires manual approval by someone in Mercury Compliance. The account in question is a SaaS for Franchisor Operations and Franchise Compliance, so we're usually considered quite low risk.. I regret losing my Mercury account, as the alternative (RelayFi) is 'good' but not as good unfortunately.