I'm definitely not ostentatious. I like to lay low and even blend into the background when I feel like it. I don't do anything purely for the sake of class.
However, if I'd go with the definiton of pretentiousness as "characterized by assumption of dignity or importance", then I definitely have that...hmm...sometimes. I am the center of my universe, after all. I don't feel like I'm better or worse than everybody else around me but, well, if I don't consider myself important, nobody will.
I don't feel like placing numbers on a scale at the moment.