Haven't had Safari crash on me I think, but then again I don't really surf much with my phone anyway. A couple times the phone itself has crashed though or behaved erratically or wonky, but it's just a bare handful - not even once a month I would say since I bought it. When this happens I restart it, and then it's fine again.
It restarts way, way quicker than my iP4 btw. iOS7 was quite slow starting up and shutting down on my old 4, on the 5S the delay is quite acceptable I'd say.
The fingerprint reader works nearly always for me. Once in a blue moon it misreads, mostly if I hit the sensor a bit too much off-kilter. I've heard if your fingers are moist it fails more easily, and if I've washed my hands recently and not wiped them off particularly carefully I too have had it fail on occation. Otherwise my hands are quite dry, but some people sweat an stuff, which may factor into its success rate, I dunno. I'm very satisfied myself with this feature, I really disliked having to tap in a code all the time when using my phone. Of course, YMMV, as always.
Overall after a number of months of ownership, some user comfort issues with iOS7's new look (like what actually is a button in some apps), but overall not much to complain about. The control center (up-swipe from the bottom) is awesome. The notification center (down-swipe from top) is also nice but could be better; it tends to hide away stuff you missed, it should show that stuff up-front without having to switch tabs, but it is still a good consolidation of information in one single place. Other than that not much to complain about, best damn cell phone I've ever owned for sure, by a large degree. It's really really snappy, light, feels great in the hand, superior build quality and materials, excellent features and battery life and so on. And with apple's superior software support this phone will be relevant for years to come.
