It's been kind of interesting, from my POV (and speaking only for myself). I had been checking out SPG slowly, since we go to Europe at least a couple of times a year, where the Ritz/Marriott presence is smaller (our other option there is Accor; we also do LHW Leaders' Club, but that is a different system). Since the announcement of the merger, we have been shifting significant business, both in Europe and in the US, over to SPG properties, business that would have gone to Ritz/Marriott properties.
What we have found is that SPG properties treat even their non-elites better, constantly, than RR treats its low-level elites at many properties. We have been greeted with welcome gifts in our room on more than one occasion because the room was not ready on time. We have been reminded at check-in of discounts available for eating on-site, simply for being SPG members. More than anything, there are properties at a variety of price points throughout the US and Europe.
Admittedly, when we want unique hotels with a local flavor and a particularly romantic stay, we tend to go with LHW, where we pay up front for something akin to elite status. But SPG has surprised us, and we will probably continue to shift business their way.