I find it interesting some of the arguments put forth in defense or against the Vancian system. Not that I find them invalid in any way, just that in some cases they seem to point towards other notions that might actually point that folks aren't necessarily discussing the likes/dislikes of the Vancian system.
For example: one school of thought is that the Vancian system is evil because it makes the casters too powerful. Certainly this isn't a new thought. EGG's original thinking was that as the game wore on, the classes progressed at different rates as part of his attempt at balance. While the Vancian system was not designed by him specifically, his implementation was certainly an attempt at balance. Taking AD&D to task for not doing the best job of implementing that balance seems, to me, to be like criticizing Watt's steam engine forty years after its invention. That is, it was the first iteration of the concept (well, OK, the newcomen engine, let's not get derailed) and successive versions, iterations and competitors refined the concept.
The innate balance mechanism was that fighters were tough at the start and got tougher, but only just so. It was easier for them to survive a fight and engage monsters. Wizards, by contrast, were fragile...the proverbial eggshells-with-hammers. Each had separate save tables and required different XP to advance. This led to the wizards being dependent on the fighters, not unlike the archers on a battlefield needed protecting by infantry...D&D did, of course, rise from wargaming roots and it shows quite well, there.
Are wizards and clerics in D&D anything like the characters in fiction they attempt to emulate, at least in semblance? Of course not. Because the needs of fiction and gameplay are not the same. Gandalf, of course, isn't your typical wizard of legend. Because excepting Gandalf, most wizards would dwell in a tower or evil crypt...they didn't go looking for adventure, they were the adventure others sought out.
The idea that vancian casters get too much flexibility begs the question: do they get too much flexibility or do other classes get too little (assuming that this is an issue)? Under 3E, a core concern was that casters could often do a better job of a task than a class devoted to that task...under limited circumstances for a certain period of time, assuming they can prepare or know beforehand what challenge they're facing. This was a problem in previous editions, but 3E codified it more than most....but at the same time, 3E was more balanced than any edition before it, in terms of player parity. This fact, IMHO, made perceived imbalances more noticeable or at the very least, more annoying. The claim that Vancian casters could outdo the fighter fell in the same place as the rogue sneak attack being overpowered, to me...true in specific instances, but not true over the long haul. That wizard could easily take out the FIRST Umber Hulk. It was the second or third that was the problem. By the time the party was escaping the dungeon, he might be spent, while the fighter was still ready for action. The rogue might have dealt more damage (with the help of flanks), but his hit points dwindled and now he had to stay back.
I liked the Sorceror an awful lot. He showed that the Vancian system could be tweaked, just like other systems. I think he also illustrates a point that I'm not sure some folks are seeing. That is, that the implementation of the Vancian system does not necessarily mean it has to be identical to previous iterations, other than a base adherence to the concept.
Consider the 3E sorceror for a moment. He sacrifices depth for volume. This typically led to sorcerors being 'blasters', but didn't necessarily have to end up that way. They could make great illusionists, for example. Because of the way they altered how they used the vancian system, they played differently...even when they had access to the same resources. A 5E vancian system does not have to mean an exact replicat of AD&D or 3E's versions. It sounds like many folks are assuming that D&D Next's implementation will be an exacting recreation of what has gone before and judging the system on that. There's nothing wrong with that, but I suspect that Monte and his team are probably looking to improve the system and make it more flexibile than previous iterations.
For me, personally, Vancian magic isn't better, but it is part of D&D's flavor and I'd like to see it included as the default. I LOVE alternate magic systems, be they rune magic, psionics, spell point systems, keywords or what have you. But if I had to choose one system that was core to the conceit of D&D (as opposed to generic fantasy), I'd use Vancian.