There are several facets of "Wizard" that I do not like in Edition 3.5. What do you mean you're not surprised? Razzberry!
Take for example the prefix "arch." Any dictionary of today will tell you that the "obsolete" meaning is "preeminent, chief." That's why so many today have no idea what the Bible is talking about when it says; "the (as in one and only) archangel."
I dislike people who desire to change the meaning of words just because they, or the people around them, cannot speak proper English. "Arch" is not English. It's one of those words/prefixes that we have incorporated into the English language. Translated into English, it means "preeminent, chief" and has had that meaning for thousands of years. Yes, thousands of years, meaning that, since you and I did not "invent" the word, we don't get to decide what it means. No, we don't.
So I don't agree that 15th level Wizards are "Archmages." No, they're not. They can't cast 9th level spells. There's nothing "preeminent" about them. There's no 17 level Wizard worthy of his abilities going to acknowledge a 15th level Wizard as "chief" among his contemporaries. Sorry, not going to happen.
So, that tells you what I think of "Archmage" as a Prestige Class. Razzberry!
And I still prefer the Spell Progression chart of the AD&D Player's Handbook, page 26. The chart takes you all the way to 29th level. From there, anyone who can do simple math can fill in the rest – though I seriously doubt anyone plays a character beyond that level. Certainly not very often anyway. If you don't continue to gain in the number of spells you can cast, why bother continuing to progress? For another Skill Point? Razzberry!
For me, this spell progression includes Cantrips, that is, 0 level spells. Why can a Wizard continue to progress in 1st and 2nd level spells, but not Cantrips? Again, there is no logical reason for this. These "abilities" are what make an Archmage an . . . Archmage! And they're what make him such a formidable opponent.
Well, just my two coppers pieces, as usual. Some of you will agree, some of you will disagree. Without disagreement, there is no conversation, so . . .