If you're photo editing then yes every screen will have a big difference after calibration
but if you're using it mainly for movies/games and web surfing then the difference is small/normal from what you'd expect from a calibration device of any sort
The Blue Eye pro is indeed said to be the best tool purely because it has the Blue Eye Pro software and this is what you're paying for because the hardware device isn't that costly at all and not really any different (if at all) to the Eye one Display 2.
The Eye One software is pretty good though and Hazro are releasing their own Calibration suite that should work with these probes just fine but give better reporting and features than the standard software (discounting blue eye pro software of course)
Mine is just fine though, no issues at all from gaming to movies, blacks are black and thanks to calibration the black details are still retained without being washed out. I'm looking forward to the new AD board as it's got a much betters scaling chip so should get slightly better IQ all round!