The movie focused mostly on the beginnings of the manga/anime where Kenshin was still trying to wander as an atonement for all his killings. Two stories from the manga/anime were merge, which was when Kenshin was dealing with an opium dealer (where Megumi was related to) and the part where a killer named Jine Udo was acting as Battousai.
I don't know much about movie technicalities. But, I know a lot about Rurouni Kenshin, and I love how the adaptation stayed close to what was shown in the anime. One of the best things I loved about the movie are the fight scenes. In the anime, Kenshin was shown to be an agile fighter. Before the movie came out, I was kind of skeptic about how they will translate his fighting skills into live action, but they did really, really great. Sanosuke's use of the zanbato (this really big sword) was also great, although he's fist fighting skills was much better.
I also loved how the castings were really closed to the manga/anime characters. Takeru Satoh was a great choice for Himura Kenshin, and even though the movie was light on comedy (which are apparent in the anime), I loved the "gozaru" and once in a while "Oro" of Kenshin. Munetaka Aoki as Sanosuke Sagara was also a great addition to the movie.
If you want a full and detailed review of the movie, go read this review by Kotaku.