i upgraded the bb first (because it started clicking after ~700 miles) then the saddle (because the stock saddle hurt) then the rear wheel (cuz I stripped the hub *and* had an incident where three spokes broke at once while I was just riding on the flat) then the pedals (because the bearings in one of them blew out) and then the whole bike. I liked the langster a lot, though, but mine was a size too small for me and when I scraped together enough dough I went for a Soma.

All in all the rear wheel upgrade was the best idea. There is no comparison between the stock hub/rims and a Paul or Phil hub and an open pro. It was a big change.