"Functional" can mean a lot of things. I think all the packs are "functional" to a degree. Sadly, I think 90% of their functionality was to power other parts of the suit that ended up not being used, like the gauntlets. As far as how functional the jet packs were themselves? We know the one shot smoke; we also know that several of the others didn't (solid thrusters). We know that one had the expanding grappling hook mechanism in the rocket tip; we also know that most of the rest didn't (solid resin rocket tip). Beyond that and the lighting beacon... I seriously doubt they had a lot of functionality. I definitely don't think they had anything like antimatronic thrusters.