In most cases yes it's by far worth it if you do any amount of traveling and especially international travel where the miles really pay off.
Originally Posted by
Alfonso XIV
It all depends on how much a mile is worth to
you, and your marginal tax bracket.
Assuming a 33% tax bracket, and an alternative account that could pay you 2.25%, you'd have to value a mile at 1.85¢ or higher for the BankDirect account to be the better investment.
Remember that the miles earned represent a tax-free return.
Some formulae worked out to analyze these accounts were previously discussed in
this thread.