I buy and sell exclusively with Coinbase.  I use 2-factor authentication with the Authy app.  I use the consumer and the merchant Android app provided by Coinbase and think they are very convenient.  I've never had a bad experience with Coinbase.

The drawback, for some users, will be their extensive requirements to become "trusted".  You have to prove your identity, you have to link a bank checking account, and you have to link a Visa credit card (prepaid and debit doesn't work) if you want "instant" buys.