I have been using Coinbase for over two years and have never had any problems with them. I make transactions via Coinbase about once a week.
The only issues I've heard of are when someone uses their addresses for casino games or sports betting.
In my opinion, this is the safest exchange on the market, but of course I never recommend keeping large amounts on web wallets.
I've used Coinbase too. If you keep anything there that you can't afford to lose, it is risky. It may be called the safest exchange, it has like 98% of their funds in cold wallets, but keeping funds in any exchange is risky. I wrote this about Coinbase specifically because it is the most widely used wallet for newbies. Anybody can easily set up an account, deposit and start using it instantly without any backups or so. It doesn't offer the keys of the addresses too. So basically, all your funds are in their hands. Why would anybody blindly trust them? I didn't have issues until the number 3 happened.