Sorry jpaul I have no experience with the Argyll software. With regards to results achieved by Color Eyes, BasICColor or Blue Eye Pro they will always be largely subjective. If CEDP creates a perfect profile to print match for 9/10 people but Blue Eye has the better match for the remaining one, then to that last person Blue Eye is the better program, regardless of whether or not it was whack for the other 9.
The justification in the expense largely comes from the technological backing and support programs like CEDP and BasICColor benefit from (They were the same program at one point before parting ways). The support is fantastic and they're trusted and recommended by industry top brass for being the best. It's pretty much worth the cost difference on it's own if you can't think of another reason. CEDP for me is worth it purely because of how easy it is to use, and how brilliantly it handles multi-monitor set-ups. Subjectively I get similar results with that, BasICColor and Color Navigator, but I use Color Navigator with my screen because it's made by the same people and intergrates seamlessly into my workflow.
If your report shows a large max delta E it could be down to a number of reasons, but the key here is to use your eyes (as obvious as it sounds - no condescending tone meant at all by the way!). If it reports a large max delta E and your screen looks wrong then something somewhere isn't working. If it reports a large delta E for a given patch and your screen looks correct then chances are the monitor and/or colorimeter just have trouble with that one particular tone. Unfortunately beyond trying multiple programs or fiddling with your RGB adjustments via the osd, there is very little you can do to correct a single anomoly.
Also remember that how a lot (I would say most because I would presume hardware DDC monitors are in the minority - Eizo, Quato, etc) of people calibrate is by adjusting the LUT of the graphics card to hit certain targets. When you do this you're essentially throwing away tones to correct others. The more you have to adjust the LUT to compensate for the screen the poorer the resulting profile will be. It's not just about colours, it's about smooth gradients (no banding or rogue colours), shadow and highlight detail, correct luminance, etc.
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