I dislike 2e's specialist wizards for two reasons. First is the creation of a universal spell list that lumps both MU and Illusionist spells into a single collection. In 1e, there were spells -- illusionist spells -- that no MU could ever cast, regardless of their ostensible school. I think 2e misreads the meaning of the schools and attempts to over-rationalize them at the expense of flavor and mystery, which is what having separate spell lists for each class did.
Second, and more damning, many of the specialist wizard types exist for no other reason than to fill out a schema. No effort is made to make each specialist type unique. Instead, each type gets an identical bonus for its favored school and cannot cast spells from one or more "opposed" schools. It's in my opinion the triumph of categorization over substance, a kind of "spreadsheet" mentality where everything has to fit in a nice little box according to an outside rationale.
I don't think 2e specialist wizards (or specialty priests for that matter) are unholy abominations and I fully understand the reasoning behind their creation. However, I think they sacrifice too much uniqueness on the altar of simplicity/rationality and, given the choice, I'd rather stick with the original presentations.
While I can sympathize with James' point of view, I can't really agree with it. In my eye, the 1e (or OSRIC since it's effectively the same) Illusionist is no more mysterious than anything else. Nor is it particularly distinct. To me, it looks just like any other magic-user/wizard/arcanist/whatever-the-hell-we're-calling-them-now: a unique spell list is but a distinction without a difference. Honestly, what fundamental difference is there between an Illusionist and a Magic-User in the PHB other than a somewhat exclusive spell list?
Contrary to James' point of view, I think the designers understood the idea of spell schools and spheres perfectly well and that the real objection, here, is that all of 2nd edition's specialists are, at their core, pretty much the same thing. They get the same bonuses and penalties, they chose from a largely identical spell list except for banned and favored schools. In essence, they were as similar as two law school students, one who focused on criminal trial law and the other who focused on corporate finance law. In exchange for sacrificing a certain level of general knowledge (i.e., they do not have the breadth of comprehension that a genarlist does), they gain a depth of knowledge in their chosen field that gives them an edge both in the lab and in the field. In the end, though every one of them works with magic of a different sort, they all belong to the same archetype and class - the hermetic/academic spell caster - and, in my mind, do not at all need to be differentiated more than that. That way lay the dreaded realm of the third edition where every fine nuance on an archetype required it's own unique base class (in some cases there or four base classes) and any number of prestige classes.
Of course, I don't object to the idea that the spell lists are too much the same. Too often, it seems that, for the most part, the spells one wizard carries are virtually identical to just about any other out there. Can't tell you how many times the later 2e modules had every single wizard NPC carry magic missile, even if the evocation school was forbidden them. Personally, I think it might be very interesting to try a campaign in which all wizards are specialists (no such thing as a generalist in this world) and they are able to learn and cast spells ONLY from their favored school: a necromancer, therefor, would cast ONLY necromantic spells. There would be a short list of universal spells, the likes of Read Magic, Detect Magic, and so on, but otherwise, all spells would be the exclusive domain of the specialists.
Now, I'm not at all opposed here to the concept of adding truly unique specialist types. As much as Vancian casting works for D&D, I think the possibility of magically endowed characters who do not utilize recipie like spells is an intriguing one. I've simply never seen an adequate example of it that would work along the lines of the D&D game (or any version of it). Maybe a simple short hand for an elementalist would be to utilize the vancian system, but to remove the "spell book" aspect and have them function more like clerics. Their spell list would be a conglomeration of both clerical and magic-user spells that would fall within that element (i.e., both burning hands and flame-strike would be a part of a fire elementalist's spell list). Instead of a holy symbol or spell book, they would be carrying a fetish or medicine bag type of object which would act as a focus for the magic.
I don't know, I'm ust spitballing here. The entirety of D&D seems built around the concept of Vancian magic (with good reason) and it's difficult to go outside of that boundary without venturing into other realms.