Coinbase handled the recent surge in traffic pretty poorly. When prices tanked / fluctuated heavily, they turned off the ability to buy citing "a lack of bitcoin" and told users they could put in buy orders now for the market price on Friday or Monday. Two days later when the price is back up to ~$700 you can mysteriously buy again.

I'm not one for conspiracy theories, but USD liquidity has been extraordinarily frustrating over the past several days since most exchanges are foreign (and US bank wires take days to weeks).

I thought we were talking about converting to cash, not buying. I agree that the hard stop on buying is extremely annoying, and that makes coinbase a bad choice for playing the market. If you want to do fast transactional orders, CampBx is probably a better choice.