I've seen it
Last Wednesday, with nothing to do, I saw this film. I thought it was a good police thriller, with some genuinely tense moments, especially the end when Matthau corners the killer in the bus. The car chase preceding it was very enjoyable, as well, but not quite as good as the demolition derbies we saw in The French Connection and The Seven-Ups.
Overall, this film lacks the pace and excitement of more action-oriented movies like The French Connection and Dirty Harry, but I think the whole point of TLP was to show police work as it really is, i.e. demanding, tedious and relying on hunches in order to solve cases.
I thought Walter Matthau and Bruce Dern were both very good, especially the latter in his portrayal of the occasionally violent, but wisecracking Leo Larsen. *SPOILER* The way in which Matthau goes about setting up, then ultimately nailing the murderer is questionable, but in the end, it helps him crack the case, only to be summoned by his boss.
I assume at the end, Martin and Larsen were commended for apprehending the killer, but reassigned for bending the rules.