I'd go see any movie that did that horrible opening weekend. You can't judge a movie by what the Lannies of the world think is good stuff. Both MIIB and xXx did some serious bank. The former was a tired rehash of a mediocre first film, and the latter is seriously on my crap list for the year. So big B.O. doesn't mean anything.
Some other huge stinkers in the past were Hudson Hawk (one of my fave underrated films!) and Waterworld (I agree with El Chuxter ) and more recently, Monkeybone, which barely cracked a million opening weekend. While not a great film, it had it's merits and got good reviews.
It doesn't cost me anything except time, I might go check out Pluto before it leaves theatres and come back with an honest assessment.