It's a decent enough overlay that my opinion of is dropping rapidly because it won't go away.
Space Mountain is my favorite ride at Disneyland. There's a very cool "abstract" nature to SM, there's no backstory or direct narrative, the thrill is simply that you're going into outer space. There's a great feeling of tension from the queue to the top of the last lift, the mission control jargon in the queue, the ambient sound effects in the loading dock, the whole sequence of the three lift hills and the power transfer and coordinate lock.
The crown jewel is the excellent music. Listen to the track and note the "main theme" melody that starts at seven seconds in. That bit is incorporated throughout the whole ride, the second lift, entering the dome, the initial "verse" after takeoff, approaching the climax, and landing, all in different variations that match the action. This is a piece composed exclusively for this track layout, and it fits the ride so perfectly that it makes the entire coaster feel "musical" like the track and music are one and the same.
Hyperspace Mountain expects us to get excited about the same tired A New Hope beats we've seen several times already, including in the parks alone. The main theme, Imperial March, and battle theme. "All wings report in", "Punch it!", "It's a trap!", it's like a greatest hits CD, we've seen this all before. The battle music is worked to match the ride well enough, but it's not a piece that was literally made for the ride like the regular theme. The new visuals are interesting enough, but they light up the building and break the visual illusion, most egregiously a crashing TIE Fighter towards the end that illuminates both the track and the wall of the dome itself. The entire cool abstract space fantasy is gone for a ridiculous "plot" involving us tagging along on a dogfight yet not really participating.
If it returned during May only, I wouldn't be as upset. It's been here for too damn long.