I'll start with my main issue. Set after volume 11 of the light novels, the anime ends with volume 7, Hoshi wo Yobu Shoujo suffers from poor character building, a broken story line and poor pacing... This movie's release should have waited for after the release of a second season of the anime, or included an extra 30 minutes or so of character and background building... The target audience may be those have read the light novels, but a large proportion of the possible audience have likely not. Reading a novel is very different to reading a manga, let alone watching an anime / movie...
For the breakdown, the overall plot was weak and though it is canon, does little to contribute to the overarching story. To me this almost feels like filler that has been aired before the void it was trying to fill even exists... This carries over to the characters. We are provided next to no background regarding the motives of Miyuki and Tatsuya except for a short flashback, which unless you've read volume 8, may create more questions then it answers. We're also "meet" Lina, and related factions but are given no insight into their backgrounds nor their familiarity with the cast we know. Without the introduction covered in volumes 9-11, we know next to nothing about Lina and that remains till the end of the movie...
If you've read up to volume 11 of the light novels, I'd say you'd enjoy it as many of the holes are somewhat resolved. In this case, I'd rate the movie a 8. If you haven't, then unless you're satisfied with a bit of fan service and some interesting but poorly paced action, I'd say give it a miss, for now.