This is my first post here. I am from /r/bitcoin. I have had no problems whatsoever with Coinbase. They have been nothing but professional with me. I started trading with them in January. I'd rather not state how much I've purchased from them, but I've had no high risk flags, just smooth sailing. I've also made one sale and confirmed that they paid my bank account.
I use a diverse selection of exchanges, as I find that each exchange has its own unique strengths and weakness, some more obvious than others.