The problem I have with Wizardry 6 and 7 is that the mechanics are ugly, particularly regen rates and base miss chance. Regen rates, for example, are determined by your starting class and never increase. Also, the rates are slow that resting to recover your spells takes way too much real time, especially later on.
Base miss chance has its issues as well. It only improves when you reach at least the highest level that you have reached before, and never past level 20. For instance, a character who levels up to 21 as a mage and then to 255 as a fighter will be permanently handicapped in her fighting abilities. On another note, a character who keeps class changing between mage and bard at the same level will eventually have a better base miss chance than someone who is just a straight fighter. To me, that doesn't make much sense, and the game doesn't tell you any of this stuff, so most players won't be able to make this decision.
There's also similar issues with hit points and spell points. For HP, I think the way Wizardry 1-5 handled them was a lot better. With spell points, the problem is that if you don't learn a type of magic until late, you will be lacking in this manner.
Wizardry 8's mechanics are a lot more elegant and transparent than those of 6 and 7. While your first choice of class does matter, it only affects HP and spell picks, and only one levels worth at most.