I'd never ever buy the Sigma SD1 at that hilariously silly price. Even at half that price. Or a third. Sigma has proven that they can't be trusted to build a real system. Quality lenses, a wide range of lenses, and a professional remote flash system, are just a few examples of why ones money would be better spent on something else.
I'll give you the flash system but Sigma is doing really well on the other aspects you mentioned.
SNIP
Kendall, the biggest shock I had when I started shooting with Canon bodies was how far behind the curve I was using speed lights. I had used one of the old EF500 flashes on my sd10/sd14 and while it worked OK I was not really happy with the recycle time, battery life, or how hot it got. It also bothered me that you were limited in the number of flashes per time period.
The old Canon 580 is light years ahead of the Sigma 500; and the new Canon 580 II is suppose to be an upgrade. Canon also has several other speed lights. But the biggest shock was when I got some Pocket Wizards. I can control multiple off camera speed lights in different zones. HyperSync lets me shoot using flash at silly shutter speeds like 1/4000 (as in using flash at one four thousandth of a second), with recycle times fast enough for burst shooting, I no longer think about battery life, and the speed light no longer gets hot to the touch.
I am reminded of my old Photo I prof saying "amateurs talk about bodies, pros talk about lens, and photographers talk about light". Giving up flexibility in lighting is giving up a lot in my book.