Before you go ahead with the floor make sure that the joists will handle the weight. I have been seeing way to many attic conversions lately that don't have big enough joists to handle the load. I get called in to do minor repairs like fix cracked drywall and spongy floors.
Once I look at the overall picture I see that they have to big a span for the weight they are carrying.
My idea of a perfect day: No where to go and all day to get there.