So if you use Coinbase and use their vault? Is it really that bad?
I believe Coinbase uses a script to send coins and sometimes it is delayed and that could cause an invoice to time out. Also, since you don't have the private key you might not be able to prove you made a payment. Usually those things are not a problem and for small amounts it is OK. I would keep a small amount in another service like blockchain.info in case you run into some issue when you are paying for something.
I use Armory because of the cold wallet features, paper backups, and "coin control" to control which addresses are used in a transaction. I use other services like blockchain.info for small amounts, when I am on the road, and to have a backup in case I am in a hurry.
