I've tried the Spyder4TV HD, and find that it does a decent job at calibrating my Vizio M3D650SV. The values it recommends are near where I had previously set them based on my use of the THX Optimizer from one of my Pixar DVDs. My one concern with the Spyder product is that while it does tell you which Color Temperature setting is closet to the 6500K standard, it doesn't quantify how far off the true value you are. The software produces a Calibration report showing a bulls-eye graph (see example below) that represent relative values to the 6500K standard (which I'm assuming the center bulls-eye is the standard), and your TVs Preset data points are shown relative to that center, but there is no value given to what each ring of the bull-eye represents, and there is no information about which colors are represented by the direction the data points take... for example, if I'm upper-right of center (as shown below), does that mean I'm too blue? ...or my green gain is too high? ...or I should offset my red??? There is no way to tell.
My TV has the ability to effect the gain and offset of Red, Blue, and Green Color Temp values, but the Spyder doesn't help to fine tune the color temp before it finishes the remainder of the calibration... Basically, it helps the TV look the best it can given it's presets, but not the best it can look overall. I have found the XML file that records the Spyder's data points, which appear to be 9 readings per record (I believe it's 3 sets of triple readings), but it would be nice to know what those values translate to.
My only other complaint (or suggestion for improvement) for the Spyder product is that for LED TVs like mine, that in addition to adjusting the standard settings of brightness, contrast, color, tint, etc., that it also accounts for the backlight setting. If I reset my TV to factory settings (under 'Standard' picture mode), it sets itself to 85 (of 100). For calibration, I set it at the mid-point value of 50, but I'm assuming that the backlight value would also effect ultimate black and white levels, so it would be nice to have some guidance on what the best setting is.