Guardians of the Galaxy: Cosmic Rewind is EPCOT's newest ride. Its premise is that it's EPCOT's newest World Showcase pavilion, with a twist: you're not visiting another country - you're visiting another planet - Xandar.  

You start your interplanetary voyage at the Guardians of the Galaxy building near EPCOT's front entrance, in World Discovery (formerly Future World East).  If you're using the standby queue, you'll be directed to doors on the left side of the entrance.  If you're using Lightning Lane at Guardians of the Galaxy, you'll enter the pavilion through doors on your right.  As at other attractions, you'll skip a lot of the pre-show elements by using the Lightning Lane - but none of what you're missing is needed for the attraction.

Once inside, the pre-show area looks like a cross between EPCOT's current Test Track pavilion and Animal Kingdom's Dinosaur: lots of walkways curved around various display items, from the history of Xandar, to the introduction of the Guardians of the Galaxy cast for those who haven't seen the movies.

The queue is set up to incorporate several holding areas - small rooms through which guests are "pulsed" through in regular intervals.  The idea here is that by switching you from lines to rooms to lines again, you'll feel better than if you were just in one long, uninterrupted line.

Eventually, you make it to the final pre-show room, where the ride's actual plot is revealed.  Like most modern Disney rides (Rise of the Resistance, Millennium Falcon: Smugglers Run, Mickey and Minnie's Runaway Railway, Remy's Ratatouille Adventure), Guardians of the Galaxy uses the "and then something went wrong" trope.  It's facile, it's tired, and it's predictable.  In this case, the thing-going-wrong is a villain stealing a very important power supply.  

Actor Terry Crews delivers the bad news about the power supply - and let me say that Terry's acting is one of the highlights of the ride; if we ever detect an asteroid hurtling towards Earth, I want Terry Crews to break it to me.  Terry tells you to join the Guardians of the Galaxy to get back the power supply.  (There are a couple of other neat show elements in this scene: one will be familiar to anyone who's been on the Haunted Mansion; the other will be familiar to anyone who's seen Mickey's PhilharMagic or Avatar: Flight of Passage.)

From there you enter the ride's loading area.  It's a large room with loading platforms to your left and your right. Both sides are otherwise identical, and having two distinct loading areas allows faster ride dispatches.  That keeps wait times low. The ride begins with a familiar ride element: a backwards launch, very, very similar to the one in Expedition Everest over at Animal Kingdom.  Then your ride vehicle turns around to face forward, at the exact moment you're supposed to enter deep space. This might be the best effect in the entire ride.  Disney's programmed the ride vehicle to spin and tilt down just a bit, as you enter a massive room, pitch black other than some simulated stars and planets.  On our first ride, we felt like we were floating in space - an actual "wow!" moment.

Much of the rest of the ride felt similar to Rock 'n' Roller Coaster: lots of tight turns past a few scenic objects.  Guardians of the Galaxy's ride track doesn't have any loops or inversions, though, while Rock 'n' Roller Coaster does.  And like Rock 'n' Roller Coaster, you'll get a rock-and-roll soundtrack during your ride.  Songs include A Flock of Seagulls' I Ran, Blondie's One Way or Another, and Earth, Wind, and Fire's September.

The ride ends with the Guardians' mission succeeding.  The whole on-board ride experience takes just under 3 minutes.  That potentially gives Guardians an hourly capacity of around 2,000 riders per hour (if everything goes right), which is better than average for a ride of this type.