Story - 8.5/10
Knocking on Heaven's Door is cast perfectly in the vein of the Cowboy Bebop series, mixing equal parts intrigue, adventure, and slick, fast-paced action with a few moments spared for slapstick comedy and character development. As usual we find the crew in pursuit of a bounty, but complications arise. What results is a struggle on a scale none of them bargained for.
The plotting is mostly very effective, though there's a few moments I caught foreknowledge apparently beamed to a character's mind by some higher power because there was no way for them to acquire it otherwise (in particular one chase scene around midway through the running time seemed rather prescience-laden).
I will also mention that the tone of the story is actually quite a bit darker than even the closing episodes of the series, and the body count among innocents is noticeably more than we'd have had in a six episode stretch of the show. It's intended to make a memorable impact in a smaller, more cohesive format and I would say that it works.
Animation - 9.5/10
All the awesome character designs from the series are present, though I don't think any of them got updated at all. Which is fine for fans of the show, really, but I think perhaps an opportunity was missed. The linework could have stood to be cleaner, but I'm not complaining when the frames are so fluid and the storyboarding and choreography are just about perfect. The action probably tops the most memorable moments from the series. It really is that good.
Sound - 9.5/10
All of the main cast VA's are back and they're as good as ever. The only downside is that since the film follows the episodic format and can't contribute directly to the plot of the main series, we don't get to experience much in the way of emotional highlights or lowlights from them. Sound effects are punchy and perfect.
The music is as good as anything Kanno has ever done, which is to say very good indeed. Standout track for me was 'Knock on the Sky', partly because it's just such a hectic rocker and partly because it's fitted so perfectly with the choreography of the fight it's set to.
Characters - 9/10
As previously mentioned, we unfortunately don't get to see much in the way of development for the main cast because of the restrictions of the format. We do see them being themselves, however; Ed in particular carries her role very effectively. Jet barely makes an appearance at all, on the other hand, mostly just facepalming his way through the script. Spike is Spike, dark and quirky as ever, but I feel like the role doesn't serve as much purpose when it's not the main focus of the story. That spotlight has been mostly transferred to the two characters whose story we're following, and they both carry it splendidly.
Overall - 9/10
For anyone who's looking for an extra helping of what made Cowboy Bebop such a success, look no further. I was struck with a fair bit of notalgia throughout my viewing and had a doofy grin on my face by the end of it. If you're not as familiar with the series, I'd recommend perhaps watching an episode or two first to get to know the characters at the least. The story stands well enough on its own, but I feel like it doesn't make a lot of sense as an entry point into the universe.