Just got an email from Discover announcing that my cash back bonus can now be redeemed at any time at any amount with no restrictions anymore.
I immediately tried it out and ordered a statement credit for 23.88 (which was below the previous minimum threshold) - I should see it in 72 hours.
This IMHO propels Discover card right to the top of credit cards with regard of ease of use of their cash back program together with Capital One's Quicksilver card. On the other hand, one of the worst is Citi Bank Dividend Card where you have to accumulate $50 in cash back before you may redeem it.