Well, it didn't go well for me on Republic last Friday. After a late (but brief) afternoon storm hit PHL, Republic cancelled flights left and right. But it looked like I'd be OK, because I could tell from flightaware.com that they had subbed out my "missing" aircraft for one that was sitting in PHL.
Unfortunately, there was no way to track my Republic crew. US seemed to think there was a crew in place, and until 30 minutes before flight time, the flight showed as "on time."
And then, for some inexplicable reason, there was no crew for the flight. The gate agents were completely baffled, and initially told us to disregard the delays notices that were being sent to our phones and were being posted on the monitors. They tried to reach crew scheduling, and couldn't get though. Eventually, they found out "from the tower" that our flight crew was still in Richmond.
Two and a half hours later, the crew arrived and we got to our destination at 3 am. Certainly not Republic's finest hour, and of course everyone booked on the flight blamed US for being incompetent. And I guess you can argue they are incompetent for employing Republic.