I am thinking on getting an I7 Imac 27" but have read of some problems calibrating the screen brightness and restricted color gamut for printing. TAzz
I use a 27" iMAc a lot and calibrate and profile it with an i1 Display Pro and i1 Profiler software (I also have other calibration and profiling instruments and software, including a Spyder 3 kit but this is the one I making the most use of currently for display profiling.) I make my own printer profiles using an i1 Pro photospectrometer and the i1 Profiler software. I've also successfully used the ColorMunki Profiler and before that the older i1 Pro and Profiler Maker Pro 5 software (with Bill Atkinson targets). I print on a variety of papers with a Canon iPF6300 imagePROGRAF. I check my prints with a a Graflite D5000 Soft-View viewer. I am pretty sure I know what I am doing with profiling on my displays and printing process.
I have zero ,zip, nada problems calibrating and profiling my 27" iMac down as low as 80 cfm2 which makes for a very match between display and print. Older fluorescent backlit 24" iMacs had problems with low illumination settigns but that is not the case with the white LED backlit LCD displays like the one in the 27" iMAcs (and probably the other new but smaller screen iMacs. The volume of the display's profile gamut also contains more of certain colors than Adobe RGB(1998) holds but there are some very saturated greens and blues which fall outside its ability to hold. the big iMac's gamut is certainly larger than sRGB in almost all colors other than extremely saturated cyans and a few very pure blues.