Bitpay, specifically, refuses to work with medical marijuana centers and so should be flogged, tarred and feathered... and boycotted.
Most financial institutions refuse to deal with them medical marijuana centers. It's really nothing personal, they just have to play it safe.
At the federal level it's all still illegal, and so if a bank provides financial services to even one dispensary, they could have most of their property (ie, the bank building, and most of their own funds) taken under asset forfeiture laws (
http://reason.com/archives/2012/11/21/drug-dealing-and-legal-stealing). It's a very scary scenario.
Dispensaries will just have to do fiat conversion themselves for a little while longer.