It's also been said that Kubrick's declining health (he died shortly after filming was complete) contributed to the length of the shoot. Clearly, it was an intense experience on multiple levels; in addition to Cruise's ulcers, this movie has been said to be the beginning of the end of his marriage to Kidman.
Collateral was a terrific film; Michael Mann created an atmospheric LA that readily accommodated both Vincent and Max. Cruise was pitch perfect in the role. It's in his top 5 of all time.