Sometimes reshoots are for the better. That is definitely the case with World War Z. Movies.com has provided a complete breakdown of the film's original ending, and to say it's different is a bit of an understatement.

Apparently the pivotal point where the reshoots took over was the plane scene. In the original film:

The plane did not crash as it does in the theatrical version. Gerry (Pitt) and his Israeli comrade, Segen, land in Moscow, where his phone (the link to his wife, Karin, and family) was taken away and he was forced to join the Russian Army against the zombies. Months pass, and Gerry is now a zombie-killing machine. Gerry's unit is tasked with clearing subway tunnels of zombie hordes. This is the first time we see the Lobo, a perfected zombie-killing tool that's sort of a shovel/battle axe that would have been one of the...