How black is the Covet screen?

Hmm, that's strange. Prcatically all standard Laptop LCDs have this greenish tone (with the exception of the higher-end Sonys), but my Covet screen, for once seems to have less of that (I haven't calibrated it yet, so I can't tell for certain). If you notice the tint, then your screen must be different from mine. Somebody in this forum had posted about such a tint, had his screen replaced, and seems fine now. You may want to look into a replacement.

Personally I found it pretty much useless, but maybe that was just me. I am happy I got a calibrator (Spyder).

I would tend to say, yes, but I am not quite sure about how the color maps work that get loaded into the graphics card after calibration; since the card itself can represent higher color depth than the monitor, you may not loose anything as far as color space is concerned. What I do know is that you'll lose brightness if you need to tune the screen heavily (like I have to on my M90).