Overall, Coinbase is reliable but there is room for improvement.
For example, instant buying through cards don't go throw 9/10 times so you have to use bank transfer which can take 1-3 days and by then the Coin prices have changed. Another downside is that they didn't actually pay out the "refer a friend" bonus. The referred friend got his bonus though so at least it's something...
For people who are just getting started, Coinbase is a trusted exchange and despite the limited Coins offered at least you get a good start without getting ripped off.