I weighed another set of wheels as well. Mine doesn't have quick release hubs, so if the new wheels had them, switching back and forth would be easier than both having just the nutted axles. What made me stay with the single set of wheels (tires) was that the tires that originally came with the bike are still good after all these years. They are also knobbies for off road that really are a off & on road knobby. Meaning the contact patch in the center is solid and behaves more like a straight line commuter/urban tire rather than a dirt grabbing off road tire. That also translates for faster rolling on harder packed trails too. I think I'm going to stay with these tires even as a replacement for that reason. One set of wheels and an all purpose tire that doesn't tie up funds and space when one or the other aren't used. Just as an example here's what I'm trying to relay:

http://www.performancebike.com/bikes...3_20000_400238

Forté Dartmoor MTB Tire With the Forté Dartmoor MTB Tire you can dart down the trail with greater speed and cornering confidence than ever before!

• Low profile design with a tight, center tread pattern delivers fast-rolling performance on hardpack trail or road surfaces
• Shoulder knobs provide excellent corning traction and stability when you pick up the pace
• 60 TPI casing is highly resistant to punctures and maintains comfort at lower tire pressures

It all boils down to what your needs are, what you want to do with it too ? For me, I'm not big on the effort of swapping, I'm frugal even with how much time and effort in that way just as I am with spending money. Getting an all purpose knobby, I'm not spending top dollar on tires either on the highest end tires.