It's a very good, solid film, but not exceptional. I thought Life Of Pi was more deserving of those shortlisted (though I haven't seen most of the others).
Danny whatshisface on Film 2013 summed up Argo really well in the pre-Oscars show, when he predicted that it would go on to become a great pub quiz question in 20 years' time:
"What film won best picture in the year that Life Of Pi, Lincoln, Django Unchained, Zero Dark Thirty, and Les Miserables missed out?"
Why look, it's a blog: