It seems to me that the radical variation in experience by people is either the result of the manufacturing process not being as "precise" as you'd think, or maybe that coupled with the cable and maybe even the monitor. Given that the snowy screens are caused by the monitor not being able to display the signal, it could be a monitor with a very close tolerance, a cable that's "too" tolerant (for lack of a better term), etc, etc, etc.
As for color quality, I also tend to think it's cable-related and also monitor-related. Here at work, I have a 2011 Mini with the Intel 3000 graphics, and a pair of "CTL" brand 20" monitors. One is on the TB port, the other is on the HDMI port using the included Apple HDMI->DVI adapter. I've had ZERO problems of any kind (knocking on wood). The picture on these monitors is surprisingly good for cheap PC monitors.
At home, next to my 27" TB display is a Samsung E2420. I thought this was supposed to be a quality monitor, but initially it looked like crap. Too bright and too much contrast. The color profile was pretty good. I did calibrate it according to the instructions, and it helped a little, but it didn't get good until I tweaked the brightness and contrast a little bit more by hand. Now it's not bad at all, but still can't compare to these CTL's at work.
I think I'll try swapping out my cable at home to the Apple-supplied one and see what, if any difference, there is.
I hope I'm making a point and not just rambling... it's early so I'm not sure.
Rob