I wouldn't worry just yet about that Shimano Freewheel. Two of our bikes came with that same freewheel. My wife's bike still has it. My commuter hybrid bike came with it as well, though i ended switching it out for a different freewheel with gears that were better suited to my commute. I didn't need the huge 34t granny cog on the freewheel. They wear well, and are able to be replaced on the cheap. Granted, the freehub/cassette is better, but I wouldn't throw money at it unless I was already replacing the wheelset, relacing the rear wheel, etc.