I haven't used Coinbase myself personally, but it does seem to be the go-to exchnage for Americans, providing your ok with providing all the relevant documentation.
once they can speed up buy/sell times, they will make btc a lot more useable on a day to day basis. spending your btc, then having to wait to replenish your btc makes it hard to use regularly
I think there will always be delays or restrictions with 'legit' exchanges because of the laws and hoops they have to jump though to comply with certain money laundering laws etc.