Thanks, Marsue...
I think the iMac native profile does emphasize blues and greens, plus a bit of added contrast overall. It gives images -- my own photos and those on websites -- a much more appealing look.
But, like most of those buying calibration gear, my interest is in getting better control over printing. The idea that I should be able to get a print which closely resembles the on-screen image is my only justification for the added expense. My concern for the apparent added color cast is that I'll correct for it, to make my photos look "normal", then find that I've skewed them totally away from the desired printed appearance. Time will tell; I'm still floundering around with this.
As to color space, yes, sRGB is the only way to go for images posted online. I usually make use of the "save for web" automated conversion in Photoshop to make a .jpg image specifically for that purpose. My camera's color space and that of Lightroom and Photoshop are both set at ProPhoto RGB, the native space for Lightroom.
If my comparisons show the canned ProPhoto profile in the iMac display menu -- or even the standard iMac profile -- works better than the Spyder4Pro, back it goes. By that time, however, I'll probably be color blind and it will no longer matter.
Michael Matthews