The purchase fees are only 4% if you use a credit card. Purchases are instant. If you pay by bank draft the limits are higher but it takes 10 days to get what you bought.

Every other exchange I've seen doesn't let you pay with dollars.

Yes, at times it takes longer to process transactions. But some of that is because Bitcoin only processes 7 transactions per second.

To say it's a scam is ridiculous. No, Coinbase is not a criminal enterprise.