So the verdict is in, although I think I still need to process the whole thing and will watch it again in 10 days or so.
It's good. It echoes the first in many ways, yet also turns it on its head. I don't think it is as "deep" as the original, or rather, I would say that it is less about existential dread and more about a journey of personal discovery. Yes, the running time can feel off-putting on paper, but the movie's actually put together in a way that allows every single scene to breathe and develop organically, free from editorial artifices. There's still plenty of action in there to keep you entertained. It evokes the atmospheres conjured up by many science-fiction novels from the 70s. In that way, it is closer to a Solaris than it is to, let's say Ghost in the Shell, for the most recent example that comes to mind.
And of course, it looks and sounds great. No, better than great. It looks and sounds awesome. A word that has lost its power lately, I know, but it is the most appropriate I can think of.