Calibration is essential! This is especially true if you burn a CD to get prints at your local photoprocessor. My friend at Costco says he sees more prints screwed up because they were reworked on an uncalibrated monitor than pictures screwed up in camera. His advice, unless you have a calibrated monitor and some experience in image processing, use the camera shot for prints.
I tried the adobe gamma setting in windows and although it improved my pics, I was not happy with the results. I balked at the cost of the full Monaco system but bit the bullet and bought it. I am very pleased with the results. I do a lot of printing at home and having your computer and printer speak the same color language really improved output without a lot of effort in time, ink and paper.
I dont use the Spyder but have have a friend who swears by it.
One final thought. Your screen will always produce a wide color gamut than you can print. If you print at home or through an outside processor you will never get exactly what you see on the screen. A good calibration system will get you about as close as you can get.
---Bob