I recently purchased an 24" NEC monitor and have decided that it's time to take calibration seriously.
My experience is more to do with color grading for video and film, so please excuse any errors if it does not apply to photography or other areas of imagery.
My simple advice is this: Don't take calibrating ONE monitor too seriously. The problem of color calibration is to keep color constant throughout MANY display devices or mediums (like paper, e.g.). It is best not to think of color calibration as an absolute science, and it might be more beneficial to think of it as a fuzzy concept.
Is your delivery objective to show imagery on un-calibrated monitors (used by clients and the masses)? Then surely the end result will widely vary from your intended purpose. The only thing you can do is to have enough experience in grading and hope your calibration is within acceptable tolerances.
Is your delivery objective a print? In that case too, the variables can only be controlled and manipulated by experience - because the greatest and most expensive monitors, color hardware and software cannot understand printers and papers. You still have to use your eyes and memory at the end of the day.
Then what is the point of spending a lot of money on color calibration hardware? Go with the cheapest possible professional solution (by which I mean one that gives you consistent results for your monitor). You will be okay, even in a professional environment.