Instant person-to-person transfers is basically only going to work if the recipient is also a GoBank member, no? Unless they're partnering with a service like Dwolla to send the money?
Speaking of, it would actually be pretty cool if I could send money with Dwolla directly from Simple :) Dwolla's iPhone app is terrible, and their web interface isn't much better.
It does look like GoBank is doing instant person-to-person transfers, which Simple doesn't have just yet (but they've said is coming soon).