We were all SPG all the time. We haven't necessarily sought out new (to us) Marriott brands for the sake of doing so, but have enjoyed additional options for some our post-merger trips. Of note, Domes of Elounda and Renaissance Beijing, both of which we really liked. Stayed at the Courtyard King Kamehameha in Kona last month. Not spectacular, but a good value in a nice location.
More than anything, what the merger did for us was open our eyes to life without SPG, which has also meant stays at VRBO, Airbnb, and non-Marriott/SPG hotels. In Vietnam, we chose a boutique hotel in Hoi An and an Angsana resort because it met our needs more than anything Marriott has. For an upcoming stay in Honolulu, we were planning our usual hotel (Sheraton Waikiki), but the price was unreasonably high so we did something we haven't done in almost a decade...Hotwire.
I guess we're less blinded by loyalty than we used to be and that's ok. We'll continue to choose Marriott hotels when they fit our needs and are located where we want to be. We used to go out of our way to be loyal. I think those days have passed.