The original Stargate movie was a real cult sci-fi classic and it sparked the creation of the TV show Stargate SG1 and went for ten seasons and this is the movie to end the Ori story arc. And it's a good ending.
Not going in to far the story arc, the Ori are ascended beings that unlike the Ancient's, who stay out of the lower planes of existence, the Ori force the people of their galaxy to worship them so that they can gain power. At the end of season 10, the SG1 team went and created a device that a old Ancient was making to destroy the Ori and sent the device through to their galaxy to destroy them. And it worked and the rest of the movie is to destroy the last Ori that had ascended on Earth and stop her from taking over the universe.
Acting isn't the best for a big budget movie but since this was made for DVD movie and fan like me know who the characters are the acting is spot on.
Music is much of the same for the show and feels like a warm blanket to fans.
Special FX in the show were great even with their lower budget and in the movie the FX are still great.
The DVD features are pretty standard including a Q&A panel at Comic-Con 2007, summary of the Ori storyline, and behind-the-scenes featurette.
Overall I wouldn't recommend the movie to non fans of the show because watchers would feel left out of the loop not knowing the back story. But if your a fan of SG1 and followed the show all the way through The Ark of Truth is a good ending to the Ori arc and shouldn't be missed.