I only have personal experience with the SpyderTV, since that's what I own. I can back up what Bandphan said about recalibrating every now and then. My settings changed somewhat after 3-4 months, and very little after that. Last time I ran it, around Halloween, the settings stayed the same.
I will point out that with the Spyder line there are different versions. I have the one made for TV's. I've also seen one made for computers, I really couldn't tell you or even guess what the difference is, when I got mine, I just went for the one made for a TV because that's what I planned on using it with. In retrospect though, I would have ponied up for the Pro version, as the one I have doesn't calibrate advanced settings. One thing that's nice is I can still upgrade the software for a fee.
Jack