While I don't really like PayPal, it is widely used and therefore you have to use it to some degree.
Here are my biggest gripes:
If someone sends money to the wrong address of yours, it is basically stuck there. You cannot send the money to your other one unless you validate it, but you can't do that with the same info. So, you effectively lose that money.
You cannot deny payments being made to an address to avoid above problem. Anyone can send payment to any address they want.
I would and have considered it safe to add funds via credit card or bank xfer. To my knowldege PayPal has never had an incident with this.