I will bring up a few things no one has commented on yet:
a) Level titles have changed to minimize overlap with other potential classes or to avoid suggesting things that are just not true of a generic M-U. Thaumaturgy and theurgy are more properly associated with clerical magic than with wizards, and necromancer is type of magic in D&D and not a general mastery of it. I'd do away with "Evoker", "Conjurer" and "Sorcerer" if I could think of good titles, and probably "Witch" as well.
b) Maybe most subtly of all I've slightly reworked the very baroque spell progression. But notice for example that I've moved a 2nd level spell you would acquire at 9th level to 7th level. That's because Gygax does have something like a pattern but he keeps breaking it. The pattern at first is that you gain N-1 new spell levels at each level past the first. So 1 new spell level and 2nd level, then 2 new spell levels at 3rd, then 3 new spell levels and so forth. The delayed 2nd level spell until 9th breaks this pattern which my revision follows all the way up to 12th level. After that the regularity breaks to delay the game breaking 6th level spells a bit, but I tend to continue this revision of moving ahead delayed spells to smooth the progression which is bumpier and more uneven in the original. I doubt anyone noticed, but the pattern is prettier to me in my version than in Gygax's. He also settles on a pattern of increasing your count of spells by 1 every three levels, where my pattern settles on increasing the count of spells by 1 every four levels, which I find superior even if it doesn't really matter.
c) No one has commented on the fact that I didn't fix the wonkiness of the XP progression of the class. The class starts out slower in progression than a fighter but then rapidly speeds up until it is faster than a fighter through the mid-levels, before slowing down to be appropriately much slower than a fighter at higher levels. But as the only class that is really gaining anything important after 18th level, I'm inclined to have it start out leveling faster than a fighter but then go slower and slower through the mid-levels since this accurately reflects its power level. There is no reason to be punishing up to 5th level and then suddenly at 6th level when the class is really taking off in power, make it level up faster until 11th level before slowing down again. I can't imagine what the thinking is. There is a period where it actually catches up to thief, which is ridiculous, or at least I think it is. Does this bother anyone else, or is it just me?