Anyone used the 650C x 28mm Terry Tellus?  I'm looking for a wider tire for the back of the XS, and there ain't much out there....  

Just to get a bit more cush for things like 300Ks and stuff...  considering the weight distribution, and my weight...

Paul - IMHO they are really good tires.  I've used them on my Aero for more than a year.  Only flat was immediately after mounting them, probably a pinch flat.  Not sure the mileage (several thousand miles easy), I've used them exclusively, other than the few times I've mounted my Zipp 404s (for racing).
http://harriscyclery.net/itemdetails.cfm?ID=2147
 
They certainly ride smoother than any 650 x 23 tires I've used. And they roll great too.  They roll as well as any tire I've used.  According to roll down tests perfomed by Jan Hine (http://www.vintagebicyclepress.com/vbqindex.html)
 
[Different link -- PB:     http://www.vintagebicyclepress.com/images/BQ64TireTest.pdf ]
 
, wider tires generally toll faster than skinny tires.  For example, see Vol. 5, No. 1 (Autumn 2006) - The Performance of Tires (Rolling Resistance Tests).  This periodical is great for any Randonneur.  

Quote from FlyingLaZBoy on Oct 8^th, 2008, 3:56pm:

 
Thanks for the heads up!  I did not know such a thing existed as 28mm 650c tires.  WHen I looked all I could find is 19 to 23mm 650c tires.  I've installed 559 mtn bike wheels on my barron so that I could roll wider "training" tires.

But at higher speeds, rolling resistance is only part of the equation. Skinny tires are used on racing bikes mainly because of their aerodynamic superiority over wider tires. It's less pronounced on a bike where the rider is lower and therefore more behind the front wheel, but it's still there.
 
I've read a couple of interesting articles that claim that with a 20 inch front wheel, the aerodynamic gain from a narrow tire isn't worth its increased rolling resistance on every day roads, and I guess that might also be true for a bike that has bigger wheels, but a lower rider position, like the X-Stream. With a high racer or upright bike, though, your top speed wouldn't be nearly as fast.  
 
How much difference wider tires make on a long ride, where you're only going to average 14 to 16 mph anyway, is subject to debate. Some randonneurs seem to opt for a bit wider tire while some don't.

Given the high probability of encountering chipseal on Rando rides in Texas, wider tires are what the Dr. is ordering...  especially since this 300K is not a "race."  I'm putting a 28mm Tellus (Thanks, Ray!) on the rear wheel for tomorrow...

Quote from FlyingLaZBoy on Oct 10^th, 2008, 1:29pm:

 
Flying Lazy Dude,  where did you acquire a tire on such short notice?
 
Terry

You guys need to read the link I provided at the beginning of the post, and possibly subscribe to VBQ.  You'll be amazaed at the rolling resistance tests.  Trust me, what you thought you knew about tires, pressure, and rolling resistance will completely change.  
 
You can go into the VBQ web site and read certain articles of past issues.  I have the past, almost 3 years of back issues.  But I don't really want to let them go for too long...