Robin Solsjö Höglund’s review published on Letterboxd:
Finally watched this too. It takes place during the main era of the show (the gang is all here) and they take on a mysterious terrorist during Halloween.
Overall this was great. It has a few scenes that drag a little bit and the music choices were a tad odd this time, but man alive, such strong characters - Spike finally gets an earned and fully realized opponent, and the action scenes when they arrive, just.. marvelous.
Also, even though it was made a few years after the main show I think it uses a lot less CGI, I almost didn't see.. any, so that's great! It doesn't look nearly as dated in that regard.
I had an audio issue near the end and I couldn't really reboot so I had to watch the last..10-15 minutes without audio unfortunately. Maybe I'll come back and rewatch it as intended but I still followed the plot and it was really good. A full on thriller with humor, action, a compelling and dangerous villain and really great traditional animation work (how I miss it).