Unlike wire transfers, ACH transfers can be recalled. So be careful when you want to do trades with ACH stuff. Even international/domestic wire transfers can sometimes be recalled too.
I have read mentioned in other threads that a 72 hour waiting period is necessary to ensure the funds cannot be reversed. I would be willing to allow a 3-4 day waiting period before I expect the coins if it would help quench some of the fears of reversal.
Thanks.