Ah, yes, Rah! Rah! We're the Best! That's what it was (affectionately) referred to over on the CO FT board by some of us. And believe it or not, it has been tempered significantly since the merger.
Obviously culture takes time to change, and CO has 20 years of a very strong self-promotion culture. That's not going to die overnight, but it's light years better than it was just 5 years ago.
As an example, CO would sell "state-of-the-art, ear-conforming headsets" on the plane, which was really a 99-cent Chinese mass-produced headset with garbage sound quality that lasted maybe a flight or two, if you're lucky. Similarly, they would boast about their "award-winning service" while making first class customers pay for some drinks.
While UA has its share of issues, and yes, they still over-hype, it's nowhere near as bad as it used to be under CO.