The biggest problem though is price stability, that is crucial when running a business with overhead.
Then you might be out of luck as I don't think that's going away any time soon. If you're quick with your exchange sells then everything should be fine.
Problem with that is, if they sell their bitcoin proceeds on exchanges they'll have to go through banks, and the banks will shut them down. Bitcoin price will not stabilize until both market cap and trade volume is much bigger. Right now it's too easy for a small-time whale to manipulate the price up and down.
Exactly what I thought was holding them back in the first place. They can accept btc, sure, but when they need to buy growing supplies, pay the electric bill, pay employees, they need fiat. This creates more work and more risk of the exchange rate going down. And still creates a situation where they need a bank, and the banks want nothing to do with these businesses. Seems like at the moment, it'd create more problems for these dispensaries.