I'd rather shoot with...
I'd rather shoot with a pair of 1.6x cameras than a single full-frame camera.
I use a 17-55mm f/2.8 IS and a 70-200mm f/4L IS lenses on a 30D and a 40D bodies. These two lenses give me excellent IQ. Additionally, I have a 12-24mm f/4 Tokina for wider stuff and a couple of "L" grade telephoto primes.
Pricewise, the two bodies are lot less less than the price of a 5D.
If I were shooting weddings professionally, I would very likely be shooting with a pair of 1DMk3 cameras. I would not consider the price exhorbitant. I had a pair of Hasselblad cameras and several Hassleblad lenses when I did my wedding shooting on film. The comparative prices of the Hassleblad equipment in those days would probably match the comparative prices of the 1DMk3 equipment today.
However, I am not shooting professionally any more. never-the-less; I demand excellent quality which I get from my 30D and 40D bodies with those two great lenses and from my additional selection of excellent glass.
Using two 1.6x bodies with the 17-55mm and the 70-200mm, I have an equivalent focal range of 27.2 to 320mm at my command with an f/2.8 aperture in my mid-range zoom and IS throughout the range. I don't miss the gap between 55mm and 70mm at all.
I also have an additional benefit in using two cameras. They are an insurance policy against missing shots - or totally missing coverage of some events - if one camera goes down for some reason.
This insurance paid dividends in July 2007 when, on the first day of a ten-day Alaska vacation, I slipped while climbing a slope and broke the 40D. Having the 30D as a second camera and backup saved me from missing documentation of that very interesting period of my life.
I am certainly not stating that 1.6x cameras are "better" than full frame cameras, just that 1.6x cameras are very viable tools which fit my needs and which will fit the needs of many photographers.