I have a 1Ds, and I find myself using the histogram display and highlight alert (pixels with clipped brightness blink) constantly, and the spot meter very rarely. It is much faster for me to take a test shot and look at the histogram than to try to take several spot readings and figure out an optimum exposure. If there is a spike on the high end of the histogram, stop down or speed up the shutter. If the highest values in the image are nowhere near the right sde of the histogram, open up or slow down.
Regarding the camera software, neither Nikon or Canon has world-beating programs; for best results, use either Adobe Camera RAW, or Capture One (if you can afford it).
If your budget dictates something in the 5-6 megapixel class, Nikon, Fuji, and Canon all have excellent offerings, and selling your Nikon glass may not be your best option. But if you can afford the Canon 1Ds, and really want the best image quality you can get for under $20,000, then selling your Nikon glass and switching makes a lot of sense. The 1Ds is currently in a class by itself in overall image quality, and it doesn't appear that there will be a serious challenger to it within the next year or so. (Unless Kodak comes out with a drop-in low-noise sensor upgrade for the 14n, but I'm not going to hold my breath...)