Hi Ralph,
I am using Spyder4 Elite by Datacolor and I am happy with the capability. Datacolor has several levels of product each with different levels of capability. More capability obviously also costs more. I have found it fairly easy to use and the results are consistent. One set can be used to calibrate all your monitors. After calibration, you can compare the results to RGB, ADOBE RGB, NTSC and full color gamut. The results of the calibration will be dependent on the quality and capability of each monitor. For instance some lower level laptops will not be able to resolve even the RGB color space and while some high end desktop monitors can resolve most of the ADOBE RGB color space. No matter what quality of monitor you have, or what calibration product you end up using, your product will be much improved and more consistent if you keep your monitor calibrated.