These sets don't encourage mixing in the way that that was meant, so that's a red herring. The point was about the experience gained when doing your own mixing, from scratch, not about physically mixing paint.
...
Other than the thing with mixing development, I think the main issues with these are:
1, the uniformity of colour they will tend to promote; doesn't matter if the results are good, they're just
one type of result, when any single colour category like yellow can be a range of hues just to begin with, but can also shadow and highlight in multiple ways (dull or bright, same hue or different hue).
2, they have a premium attached to the price.
3, you can't fill gaps individually.
Re. 2 and 3, since you're sure to use up one colour more than others over time this means that not only are you paying over the odds for paint already, you're eventually having to buy the equivalent of eight or ten paints just to stock up on
one colour. Yes you will eventually use them all if you continue to use the set, but just at the time instead of having to fork out two bucks to be able to continue you have to pay many times that amount.
Previous discussions for anyone interested:
http://www.planetfigure.com/threads/andrea-releases-new-easy-paint-red-set.29414/
http://www.planetfigure.com/threads/andrea-paint-sets.44360/
Einion