These are problems, but they aren't insurmountable problems. One of the things which changed my mind about bitcoin a bit was seeing all the damn clever stuff they've come up with - paper wallets, offline transaction signing, etc. Yeah, if my machine gets hacked, I may lose what's in my desktop wallet.. but presently, that is so little that it's an acceptable price to pay to find out I've been hacked ;)
About exchanges, you know what Bismarck said ... Those who know how laws and sausages are made, do not like either. There's a lot of shoddy security in our conventional banking system, too. Think about credit cards, about how rotten security they actually have if you look objectively on it. With bitcoin, I at least know there's some really smart cryptographic design at the core of it.
You can't be sure. You can never be sure. The question is what risks you're willing to take. Right now you (and me, and everyone else) trust a lot in "too big to fail", or "too many to fail" - that we're in the same boat as enough people, or enough powerful people, that if something gets messed up too bad the powers that be (government and non-government) will set it right. To avoid food riots if nothing else.
Wouldn't it be nice with a little more decentralization, a little more democracy, a little more trusting in math than trusting in the self-interest of a powerful few? Bitcoin is at heart an experiment in distributed consensus-mechanisms. It's an interesting experiment.