I have Sora on a low-end bike, beat it up pretty good over the past year, and it's still fine. The little red arrows are now out-of-whack, but I "know" what gear I'm in anyway. If anything is ready to catastrophically break, it's given me no indication. I keep the cables tensioned correctly, ensure everything is tightened, etc. basic maintenance.
I have no problem with the thumb shift. Sure, you have to move your hands if you're in the drops, but so what? It's a minor inconvenience. I have another bike with 105 shifters, and while I will definitely say 105 is superior, I won't say Sora is terrible.
One thing I like about STI in general (at least most STI - this won't apply to some Dura-Ace and Ultegra) is the ability to mount a Mirrycle STI mirror. In my opinion, that mirror offers excellent rear visibility without looking out-of-place on your bike.