I have the 17-55mm f/2.8 IS lens and absolutely LOVE it EXCEPT for that darn 55mm wall which is frustrating at times. However, this lens provides excellent IQ, great AF and extremely good IS.
The 27.2 to 88mm equivalent is fairly decent and was the approximate range of many of the manual focus mid-range zooms of yester-year. Sure, I would like a longer focal length, so I often carry a 70-200mm f/4L IS lens which I selected in lieu of the 70-200mm f/2.8L (series) because of the lighter weight and more compact size. The f/4L IS lens AND A SECOND 1.6x CAMERA weighs about the same as the f/2.8L (series) lens alone.
Yes, I have often thought about a single lens which will give me the range that I want but, I am very fussy about IQ and I am often hand-holding my f/4L IS lens at 200mm where the extra stop (f/4 vs. f/5.6 at 200mm) can be quite important.
I just bite the bullet and carry the two cameras and two lenses. That way I have the 17-55mm and 70-200mm range at my finger tips. I don't miss the 55-70mm gap between these two great lenses. The combination might be bit heavier than I would wish for but, still very much within reason.
An added bonus is that I divide my shooting between the two cameras; usually about 2/3 of my imagery from the 17-55mm and the remaining 1/3 from the 70-200mm lens. That means that I almost never run out of juice in my batteries, a single CF card for each camera (16gb) will most often suffice for a day's shooting and, most importantly, the second camera provides insurance against missing photo opportunities due to camera failure.
I fell on a slippery slope during a ten-day trip to Alaska's Kenai Peninsula and broke my 40D camera. My 30D which I had with me saved the photo opportunities for that vacation. Conversely, a fellow tour member fell on the cobble stone street in front of the Xi'an, China City Walls and broke his Nikon DSLR. Having no backup camera, he missed out on photos (including those of the Terra Cotta Warrior Museum) of that trip until he arrived at Hong Kong where he could buy a replacement camera.
BTW: the Optech Dual Harness makes carrying a pair of cameras easier because it distributes the weight across my shoulders rather than hanging from my neck