I got Sony's first generation Alpha ( formerly Minolta) a few years back, along with a couple of higher end lenses. I'm fairly happy with it, but find that the color is the hardest to get right. I'd like to upgrade to a Canon/Nikon in the future.
Upgrade? Why not "upgrade" to the Sony Alpha 700 or even 850? If you already have decent glass, changing systems is a complete waste of money, IMHO. I'm sure you can find people who use Canon or Nikon that will tell you different, but I'll bet none of them have used Sony's newer cameras (A700, A850, A900).
If your problem is color, shoot RAW and learn to process photos or adjust the settings in camera.
Honestly, if you gave me the money to do so, I wouldn't "upgrade" to the Canon or Nikon systems. They are great camera systems, but they aren't superior. I've used all three brands of DSLR ( Olympus and Pentax DSLRs) and none is superior. If you already have good glass, changing systems is throwing money away unless you have a real concrete reason to take the loss.
Chris
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Chris Harrison
San Antonio, Texas