Watched this two weekends ago, and really enjoyed it. Pegg and Frost are great, as usual, but I thought the other guys were also up to the task. The story starts out great, and then takes an unexpected twist. Frankly, I'm not sure if the twist really added that much to the movie. I enjoyed the first half of the movie just as much as the second. The dialog is filled with they typical witty banter, along with the typical sharp barbs.
It was a fun ride, and I'm sorry to hear that this is the last feature in the Cornetto trilogy. I'd rank it second, right behind Hot Fuzz.
With luck, the three of them may come up with another trilogy in the future.