As always, the selection of the Illusionist, as a single class character, requires a far more intelligent and capable player, than say... an evoker, simply because one must understand how the spells work, and how to best manipulate them, because they often do not give direct control limits. Damage-dealing spells are straightforward; cast --> effect. Not so with an Illusionist, who has to actively seek to generate the desired effect. This, in turn, requires a DM who has the capacity to adjudicate the results within game reason, and not turn the potent abilities of the class into something moot and useless. If the Wizard is the "thinking-man's class" then the Illusionist is the "magna cum laude." It requires flair, style, wit, and a deep understanding of the nature, and the lack of such, in everything around the character. Everything, to the properly played Illusionist, is a lethal trap, a weapon to be added to his already wonderful arsenal. This, again, is why the class, often is mixed with another... especially something like Rogue, or in the case of pre-3.X, Assassin, due to the boosting capacity the class provides. It has been retained throughout D&D, but the showmanship has been dwindled, mostly because the powerful spells, the "save or die" effects that used to be present, the ability to cast any Wizard spell (up to a certain level, gained at a certain level), has been lost. It is a shame to see the class treated as discarded refuse... but, to me, this means the class has not changed, but the class of the gamers.