Vancian Magic is okay as far as it goes. As a mechanic, I don't think it works very well. The real issue isn't so much that Vancian Magic 'sets itself apart' from all the other mana based systems out there, it's that so many people have absolutely no comprehension of how the system even actually works. In many cases, this includes those arbiters known as the current IP Holders.
Why? Because, Vancian Magic, as a system, is counter to all that we are exposed to in terms of how magic is 'supposed' to work in all the other literature (includiing mythological and historical references,) and thus percolating into all our other forms of media.
So, if it were to make any real sense to all, it must be explained, to a better degree (and it's origins referenced) in the D&D manuals. Sadly, this is not the case.
I, too, am a fan of Jack Vance's writings. I never, though, came across the particular book that his magic system's framework was pulled from by Gary and Dave for D&D. And, years since I have been told where it came from, I still haven't been fortunate enough to then come across that specific book title to give it a read.
I'm sure I would enjoy it.
It doesn't change the fact that I think Vancian Magic is whacked as a system to use. I have hated the whole Memorize, Use, then DOH! I can't cast that spell again mechanic. It just doesn't bear out logically, in my mind, as a framework that would allow for such powerful magics. And the levelling thing? Well, that's more the mechanics of D&D, I am sure, than it is specifically of the original framework. Then again, not having had direct access to Jack's story from whence comes the system, I cannot accurately say.
I see magical energy as more akin to 'all those mana systems' out there that are similar to each other. I think the most important part of the 'failings' of those other mana systems is two-fold: First, and possibly most importantly, D&D is the prime RPG from which all others were derived -- in terms of it being the First RPG, and thus from it, all others are derived, conceptually. Second, game mechanics are hard enough to do for 'real world' physics and actions, so adding in magic, without taking a goodly amount of time to examine how your desired "Magical Framework" is supposed to function tends to make something that is easily exploited and spammy; in the sense that it makes even lower level magic casters waaaaay too powerful for their overall level of experience.
D&D's magic system is, IMO, deeply flawed in some basic ways. These flaws have been there from the day magic was introduced as a mechanic in the game. And, like Ptolemaic Cosmology, instead of being ripped out, restudied and re-examined for those flaws, the following upgrades, updates and revisions have done nothing more than add further complex reasonings to 'explain' and support the flaws' observed discrepancies, rather than allow some young Copernicus' logical system to take it's place.
All that said, though, it does work in it's fashion. And, as I have played D&D since 1978 (though it really didn't take until 1981 -- long story) and have been designing my own gameworld since about that time as well, you could say I have some definite memory and familiarity with the overall use of Vancian Magic. I play it, I use it, and it can be fun as part and parcel of what D&D is.
Were I to make my own Rules Set, though, I would not use Vancian Casting -- at all. Not even a little bit. I would not use it to sink a boat, to polymorph a goat, to break into a house, or change into a mouse. I can not, will not use Vancian Magic, Sam I am, I can not, will not have it, even to avoid the spam.
And, in the words of Forrest, Forrest Gump, "That's all I have to say about that."
dunniteowl