I left FlexJet over 3 years ago so I guarantee that my info is out of date, but here is what I remember:
-red label was pretty amazing but you have to interview for the position (which did not honor seniority) not sure if that is still the case. It's one of the reasons I left, I know pilots that were hired with me and 1 year later he was on a Red Label Gulfstream team as a CA, bypassing at least 15 years seniority. AGAIN not sure if that is still how it works.
-they voted out the union, which benefited the most senior pilots... when I left it was a very toxic environment.
-you work your ass off....beyond flying the airplane you do EVERYTHING (cleaning, carrying and loading bags, catering) my 2nd year back in 121 flying an airbus I made more and worked almost 1/2 the days as I did at Flex and never turned right on the airplane.
-when owned by Bombardier you were treated as an asset, when DAC bought them you were treated as a number, I hear this has gotten better.
FWIR, pilot pay was about 100k for FO's, 150K for CA's on the Challenger, Red Label was about 200-250K depending on bonuses and extra days flying, Red label teams consisted of 3 pilots all Captains and they would utilize a non RL First officer. if needed I'm told upgrade is about 1-2 years on the Phenom and 5+ on anything else. I know pilot pay has gone up but not sure what it is now.
Flexjet was better than the regionals but a far cry from the majors (red label can get close but good luck on that)
I mostly miss the food, destinations, and the type of flying!