Of course, 100% reliability probably doesn’t exist in the HA world, but the ST platform seems to have more than its fair share of problems. I’m not trying to scare you off of ST, but a quick search of the forums reveals a notorious history of ST user/community issues. The latest:
Personally, I’ve had no serious problems with ST, overall — just some missed firings of scheduled routines every now and then. But my automation needs are fairly simple and straight forward. Even so, it does get annoying when something doesn’t work when it should. For example, I have simple routines that control my landscape lighting — one failed to turn on my front landscape lights two days ago; one failed to turn off my backyard landscape lights three days ago. Those problems where probably related to the ST backend/server issues mentioned in the above threads.
Anyway, what I was sort of getting at in my first post was to probably avoid automating certain aspects of your home that may have severe consequences because of ST unreliability — if you fully automate your front door or garage door, you might return home to find an unlocked door or open garage door. Having said that, there are individuals (like @JDRoberts) who fully rely on HA, so yeah, needs vary.
Automate with ST, but your second job will be a baby-sitter. Of course, you probably can’t go wrong with automating lights first … maybe, hopefully, sort of 
BTW, I need to buy more Z-Wave GE paddle switches and outlets 