Wow, great debrief and congratulations!
I'm stuck at the 690 threshold atm.
Despite what you said about Knewton lacking in regards to quant explanations, I've been considering purchasing it due to the 50 point guarantee they offer--especially considering that a 50 point improvement would put me at a whopping 740.
I have completed the MGMT program (self study) and originally thought that I had made huge strides in my quant, but for some reason I didn't make an improvement on test day (stuck at a Q43). I'm looking at Knewton for some extra CATs and maybe a different approach to studying. After all of the frustration I've experienced thus far (taken GMAT 4 times), I'd most definitely be willing to pay the $690 for Knewton if they'll guarantee that I'll raise my score to a 740. A 740 GMAT score is 30 points higher than my original goal of a 710, so even if I can improve just 20 points (710) and get my money back, it would be just as worth while! But I really need to improve my quant score up from a 43, I guess I need to research Knewton a bit more to see just how strong it's quant expertise is.