We've had mixed success calibrating monitors with HDMI connections. This is less of an issue with newer graphics cards that have multiple DisplayPort outputs. Dell monitors worked almost perfectly, with brightness needing manual adjustment over HDMI while it was software controlled with DP. NEC monitors also worked with the caveats mentioned above. Eizo panels were just a pain, always losing the EDID key with a HDMI cable, making for both crappy graphics and poor calibrations.