Got a set of Primo Comet Kevlar 20 X 1.35 tires:
The silver reflective sidewalls look very cool with the silver paint job!
The Xootr Swift is spec'ed with Kenda Kwest 20 x 1.50 tires, and heavy-duty Kenda 20 x 1.50/1.75 tubes. A pair of Comet Kevlar 20 X 1.35 tires are 276 grams lighter than the Kenda Kwests (about 0.6lb), and a set of 20 x 1.25/1.50 Pyramid tubes feel about half the weight of the stock Kenda tubes. I'm estimating that by merely changing-out the tires and tubes, you can shave almost a whole pound of rotating weight.
Durability has been excellent for the week that I've had them. I actually nailed a pretty big rock (looked more like a chunk of busted concrete) at 22mph yesterday (in a bikelane, ofcourse....bikelanes seem to be magnets for debris) that ricocheted from under the sidewall, pinging the front rim on exit. It sounded so bad that I pulled-over, certain that I had gotten a sidewall puncture. No damage to the tire and no puncture. Excellent.
The Comets also ride better than the Kendas. At 100psi, the Kendas have a bone-jarring ride...I usually like to ride them at about 85psi, but at that pressure, I can feel the rolling resitance. At 100psi, the Comets feel a little more supple, yet roll fast and with noticeably less resistance. You can really feel the difference especially in out-of-saddle sprints, where you're trying to get the wheels up to speed as quickly as possible, as well as leisurely coasting, where the Comets seem to roll farther before needing input from the pedals.
It's stated on Xootr's website that they spec the Swift with "bulletproof" tires and tubes, which I have to agree...they've been indestructible...but if you want to inject your Swift with an extra dose of zip-zing, then definitely upgrade the tires. You'll get more speed-per-buck in a tire/tube upgrade than any titanium bolt-on bling.