My measurements:
Outside Dimensions: 21.25x15x7.5 inches
Inside Dimensions: 18x13.5x6 inches
Pocket Dimensions: 16.25x12.5 inches
Weight: 6.6lbs

I'm getting the most important information out up front, as the primary reason one buys a carry-on this small is to meet the increasingly-restrictive qualifications of international airlines. The official dimensions of this bag have it as 20 inches long, but it is really 21.25 to the handle strap (as specified by the airlines), and this is not with the strap extended. The height is closer to 7.5 inches, and it could be higher depending on how much you stuff in the bag. The weight is pretty good for a bag this size, important as many airlines restrict carry-ons to as little as 12 pounds!

Be aware that Victorinox has an almost identical version of this bag with "WT" in the model name.  The difference is that the WT has a fold-out garment carrier in the lid and it weighs a bit more. Several sites where I found this bag listed combined the WT and non-WT bags in the same listing, or used photographs of the "other" model. I have attached several pictures showing all views of the non-WT bag.

The outside of the Werks Traveler bag is well-constructed, with rubber strips and bumpers at many potential wear points. All zippers are metal and one keyed TSA-approved lock is provided. On the outside of the lid are two zippered compartments.  A small one holds part of a strap system that, combined with a strap in the other outside pocket,can be used to attach one or two other, smaller bags to this one (see one of the photos I attached.) The larger compartment is generously sized and would hold a 15" laptop, though the padding on top is minimal. There is a flat mesh pocket on the inner lid of this pocket that seals with two Velcro patches.

The main compartment has adjustable Y-straps to hold the contents down and a non-detachable mesh pocket in a flap that folds down inside the compartment.  The inside of the main lid is plain. The main shell has stiff inserts around the bag, with good protection for the contents.

The T-handle stores in a zipper-closed compartment and telescopes out longer than other similarly-sized bags.  A nice feature is that the handle can be rotated 90 degrees by pressing the unlock button.  This button is also used when you want to collapse the handle.  The handle is comfortable and shaped, with rubber grips.

I have to say that I don't quite understand how luggage manufacturers can command such lofty prices for rather ordinary luggage, but at least the Victorinox Werks Traveler 4.0 Ultra-Light is well-constructed with some useful features and appears reasonably sturdy.  You could check this bag and it would not be any worse than bags not intended as carry-ons.

Edit: 6/3/2012 - We just returned from a vacation in France where we took the Victorinox. While it fit (just!) in the overhead bin of a Lufthansa A340, we had to "gate check" it on the leg where we were on a regional jet. And on the trip home, we checked it all the way (as we had an extra "duffle" type bag for souvenirs. I am happy to say that the Victorinox acquitted itself well, coming through with no problems. My wife was very pleased with the packing capacity - unlike many similarly sized bags, the Victorinox has square, not rounded, corners, and every cubic inch counts. In fact, we liked it so much that I bought the&nbsp;<a data-hook="product-link-linked" class="a-link-normal" href="/24-Werks-Traveler-4-0-Suitcase/dp/B004MKLU76/ref=cm_cr_arp_d_rvw_txt?ie=UTF8">24" Werks Traveler 4.0 Suitcase</a>&nbsp;- see my review there.