We've been using Stripe ACH's payments for a couple months now (coming from Balanced), and the whole process, from charge to bank, takes around 7 business days, and the statement shows up on day 1.

I consider this a long time, so long, that I'm actually considering on working directly with a bank myself and plugging into ACH network directly (The way we operate, its faster for some clients to just be paid through PayPal and cashout through PayPal).

As far as fraud goes, ACH charges can be reversed with no questions asked for 60 days if it turns out the charge was unauthorized (with no recourse, except asking the customer). On the other side, if a fraudster has your bank credentials, and can confirm with micro deposits, this is no different than them going to PayPal or Venmo with that same information.