I haven't seen a significant change to me personally. I didn't experience the IT issues that many people did, and the cut-over and subsequent point posting, etc. worked fine for me.
I've appreciated the additional properties, and have stayed at a SPG hotel a couple times where I would have, in the past, gone a few more blocks out of my way to book a Marriott. Service at the properties hasn't felt any different to me.
I don't like the rewards devaluations, but it's possible those would have occurred anyway. I like the fact that I went from no LT status to LT Plat under the new program, and also appreciate the SNA's. I've used them on one stay so far, successfully.
I rarely have a reason to use customer service so haven't experienced those issues. The one time I did, while I was walking through IAH after a cancelled flight, I got right through to a rep, who was polite, friendly, and helped me get a room at the nearby Sheraton, using one of my free night certs...all while I was walking toward the airport door.
Some of the SPG lounges have been disappointing. At the above-mentioned Sheraton, I stopped in for some kind of quick dinner. At Marriott, that would be an array of appetizers and probably one or two more hearty dishes. At this lounge is was a big vat of spaghetti and meatballs and a veggie tray. Disappointing. But that can vary from property to property.
Overall, I'd say there were some minor pluses and minuses, but mainly a big non-event for me.