The only way through that is experience and it's not entirely different between the OS's. Some apps are well reputed, others hose your system. It is difficult to know what can be trusted, which is why the extras repo was implemented. As has been mentioned before, if you stay there you should have no problems. I wish you well with your Vaio. Not sure why you're refusing Apple hardware out-of-hand; they've appeared less draconian of late than Sony...but that's clearly subjective.