I need a two baby jogging stroller and I've been told time and time again that BOB is the best.  I never did buy the single baby jogging stroller, so all of the fixed vs. swivel wheel is new to me too.  Also, the car seat conversion thing.  Is it worth the extra money?  Is the Ironman or the Revolution model better?  I like to run mostly on the street, but there are occassional sand/dirt/gravel trails that I go on.  Any advice from someone who owns one is helpful.