Transactions are nearly instantaneous, less than a few seconds and they'll reach most of the network. With fees, once that occurs, the circumstances where they wouldn't confirm are few. Confirmations, as DH said, take an average of 10 minutes. In most cases, for low value transactions, zero confirmations are acceptable.
For high value, confirmations are always recommended, the higher the value, the more confirmations in my book.
There are many situations where even high value transactions can be accepted with 0 confirmations.
As long as you have a trust relationship with the payer, or a very high ability to repossess the product or service that was exchanged, there is little need to wait for confirmations.
True.