The show was great, but a lot of what made it great (IMO) is the real time aspect. I am not sure how I would enjoy the movie. Sure the established characters might be there, but the whole point of the show was to give us a full day as it pans out. Otheriwse, it will be like any other movie that condenses a day into roughly two hours. If a movie does come out, I will likely see it, in hopes that they give Jack some form of closure finally. If they make it open ended for a second and third and God knows how many others, I will likely skip it.
The thing I didn't like is that every season was about terrorism. On top of that, there was always a mole in CTU. Every season, there was a mole. One would think that they would learn after the first handful of failures. I don't think we have had this many mole terrorists in the history of the US, but with Jack Baeuer to save the day I suppose we can afford it.
On a side note, "The Confession", which is on Hulu exclusively right now is fantatic. It stars (and I believe is directed by) Keifer Sutherland. Looks a little lower budget, but I find it great. Reminds me a small bit of what 24 meets Boondock Saints might look/feel like.