I think we need a modified Vancian system to really bring people back together. The features I liked about Vancian Casting were the limits you got to push each time you leveled - mostly the idea of access (adding to my spell book, gaining a spell-level) and less the idea of capacity (limits to how many times I can participate meaningfully in a day).
Breaking Spells up into Greater and Lesser Arcana appeals to me. A Wizard shouldn't stop being magical and turn into a pumpkin when the clock strikes Noon in the adventuring day. Cantrips and basic attack and defense spells a Wizard knows by heart and can create with minimal effort are his Lesser Arcana.
His Greater Arcana require components, foci, and ritualized preparation and memorization from his Spell Book each morning - so his relative power (experience level) dictates just how many different Major Arcana he can prepare for each day.
Greater Arcana are also draining. A Magic-User is limited in the number of Major Arcana he can safely manifest in a short period of time (such as an individual battle). A Wizard exceeds these limits at the cost of draining his own physical and psychic reserves (healing surges). He might also do so making an exertion to enhance a particular spell or such could be the innate price of a particularly dangerous or complex ritual.
In this way we keep some of the most sensible aspects of Vancian Magic, and finally get the fantasy aspect of how overcasting (Raistlin from Dragonlance, Telah from Final Fanasty) can be land one on death's door.
As a caster unlocks the higher mysteries of the universe the relative definition of "Greater" and "Lesser" Arcana shifts, so at some point in his evolution (maybe when he makes a particular Tier) what was once a "Greater Arcana" for him now becomes part of his collection of "Lesser Arcana."
Because seriously, once I started start dropping 7th level spells it really didn't add much to the game that I still had to engage in elaborate book-keeping for a bunch of level 1 and 2 spells - many of which didn't even scale meaningfully by level!
I think the problem with both the Vancian and post-Vancian spell-casting models is they were all about telling people "No, you can't do that," instead of saying, "Yes, you can do that, but this also happens."
- Marty Lund