I thoroughly enjoyed the S3 premiere. It took me a bit to get back into the swing of things, remembering who was who and what was what, but once I did the show's vibe felt much the same as before, and that's a good thing. it struck a very nice, taut balance between action, narrative development, and character moments. (Indeed, on that last front, the writers and actors make really effective use of downright minimal bits of dialogue and interaction to convey some strong emotional beats.)
I haven't read the books the show is based on, and I don't know how much it deviates from the source material. I can certainly say, though, that it seems like there's a clear long-term plan for the plot and the characters. And every time the stakes get raised (or changed), it seems like a logical, even inevitable development of what's been set up before.
Plus, the show just looks fantastic. I wish DSC looked this good.
At the end of the day it's still space opera... but it's mature, intelligent, thought-provoking space opera. Can't complain about that.
(Honestly, my only real gripe about this show is some of the accents. I often feel the need to either rewind a scene or put on the captions just to make out what certain characters are saying.)