Sebastian has a posting on using competitive shooting sports as police training. Good stuff all around and I think the main article makes all the relevant points. I’ve been wanting to get into competition shooting (IDPA or IPSC) but so far the schedule just hasn’t meshed for it.
What I wanted to comment on in Sebastian’s article tho was his comment that “you can’t really practice real gunfighting”. While you truly can’t practice this (or at most you’d only be able to practice it once :D), I’d say what gets you closer than anything would be force-on-force training.