I recently saw some posts about the perennial subject of Vancian spell casting and whether it made any sense for a magic-user to forget a spell after casting it. I've talked about my views of Vancian magic before, but since I've been watching a lot of reruns of Buffy/Angel, I've been comparing the way magic works in supernatural dramas to D&D magic.
A witch or wizard casting multiple spells in an episode of Buffy or Angel (or Supernatural) is pretty rare. In fact, if there's going to be a spell in an episode, researching the spell, locating ingredients, and completing the ritual frequently takes up half the episode or even the full episode. Of course, most of these are major rituals to either stop the Big Bad or bring about an apocalypse, but you even see this for small spells cast in some cases. Willow, at the beginning of her witch career, has trouble completing one simple spell like light or levitating small objects in a single episode. As she gets better, we may see two or three spells in an episode, plus one big ritual. It takes a while for the series to get to the multiple rapid-fire magical duel between Giles and Willow, and that is clearly presented as being unusual. Even there, the duel involves fewer "spells" than a 12th-level magic-user would be able to cast.*
* (I picked 12th level because that's when a by-the-book LBB magic-user can cast spells of the highest level, comparable to the most powerful spells seen in the series.)
Of course, magic in supernatural dramas usually takes longer to cast than a Fireball in D&D. But then, prior to AD&D, spell casting doesn't involve much ritual, either; it's usually treated as a simple gesture and short phrase. The way I picture it, OD&D magic *is* a lot like spells in supernatural dramas, but the ritual part happens "off-screen"; the magic-user performs a ritual that links magical forces to a gesture/phrase combo, and making that gesture while speaking that phrase completes the final stage of the ritual, triggering the magical effect.
In other words, spell "memorization" isn't memorization, but preparation and ritual. All that's being memorized is which gesture/phrase combo goes to which effect. More powerful magic-users can prepare more spells in advance, making them more effective.
So, Vancian magic doesn't seem all that "unrealistic" compared to magic in supernatural dramas. What it can't do so well is emulate magic in supernatural comedies, like Bewitched, I Dream of Jeanie, or the various incarnations of Sabrina the Teen-Age Witch, where magic is fast and loose. Little spells like telekinesis or levitation are as trivial as opening a door, and you see lots of 'em in a single episode; big spells are more limited, and you usually see only two big spells an episode: one that creates the problem in the episode, and one to fix the problem. Occasionally, you'll see more big spells, but these will be failed attempts to fix the problem. So, even a limited beginner from a supernatural comedy would be a difficult challenge for a 12th-level D&D wizard, or for an experienced witch/wizard from a supernatural drama, and even "dark-side Willow" would be no match for someone like Maurice or Endora. For *that* kind of magic, you need something like the psionics rules or something even looser.