Overall I thought they did a good job with the amount of time they got, which was less than a year to push this through production and post production. That probably explains the mediocre CGI.
Non sequitur, but here's an article with Mathew Vaughn.
I didn't know John Dykstra did the FX work on this movie. He also did FX work for Star Wars. And I almost forgot Vaughn was attached to direct Thor early on.