Just got back from my trip, I was able to ride this three times thanks to a combo of I.L.L. and boarding group for one day and getting another I.L.L. for the second half of another day.
To get the elephant out of the room first, I'm not one to get motion sick. Really the only time I did was when I tried playing Mario Kart on DS during a car ride. But for me, I can handle all sorts of coasters and spinning rides with no problem. For my first ride on Cosmic Rewind, I actually got a tinge of motion sickness. I think it might have been a combo of a near empty stomach and my eyes/head trying to follow some of the projections on the ride. So that had me a little nervous, but then I went on the orange version of Misson: Space right afterwards and felt just fine. (And I don't get sick on that ride, and I've done everything they tell you NOT to do.) But then on my next two rides with a fuller stomach and not trying to follow the projections, I had no issues whatsoever.
With the whole experience, I think it makes a great case that the term "Story Coaster" should be slapped out of the vocabulary for ride designers. There's really not much of a story here, and it sure isn't told during the coaster itself. There are some ideas here and there, like with the whole "Wonders of Xandar" pavilion, but I agree with
@Joe that if you wanted to push that edutainment angle, showing how various real-life things are similar with those on Xandar would've worked perfectly for that.
As for that teleporter, that was a lot of build up for something that was nowhere near as impressive as the Transporter effect from the defunct Star Trek experience. Though I do find it funny that since there's nothing to keep everyone looking forward, most folks are facing backwards for the effect, so it ends up having no impact with the reveal.
That said, I do like the addition of Terry Crews, he does bring in some great humor. And with the coaster itself, it's really fun! It does pull off some fun maneuvers throughout the ride, and it can also pull off some really cool lighting effects such as the re-entry at the end. That said, the projections could be a tad nicer, and I do agree with
@Brian G. that I'm not fond of how you can pretty much see the building in the launch area.
Song-wise, I only got two. I got Conga twice, which I didn't mind since that's a good high energy song for the ride which works quite well. The other song I got was I Ran (So Far Away) and I downright LOVED that one for the ride. Watching vids of the other songs, I think I did end up getting some of the better ones. Though I will say I would've liked to have experienced Everyone Wants to Rule the World since that song is uniquely mellow compared to all the others.
Another thing to mention is I appreciate the rides has extra dialogue moments in case of a slowdown etc at both the lift hill and the launch area, I ended up getting it my first ride at the launch area, and it gives a nice 4th wall joke. Plus it made for a better surprise when the ride did launch!
All in all, it is a really fun coaster, but as a Guardians ride, personally I would put this under Mission: Breakout! at DCA which I feel is a more solid experience overall.