Interesting idea, will see how it goes, card hasn't been sent out yet so i can't say how good or bad the service is.
Would love to utilize this but until the cards roll over from month to month I will be steering clear. Sure a few unused cards may not sink any business but the principle behind charging in this manner speaks volumes about the character of the company. Luckily other developers are working on this type of application. It is much needed without doubt.