Agreed. And inspiring false confidence like the thing Fitzy posted is almost as bad as ignoring your kids self esteem. Because then they'll think you were just a 'loving parent' and they don't trust your praise in any way.
Hell, false confidence can also be easily broken by any bully and seen through by anyone smart enough. Just get your kid to know that's he's got it right, whatever it is... make him know he got it.