Nice to see my thread's gathered some momentum. First off, I need to precise some things: I haven't done anything to alter the game mechanics of spellcasting in my campaign: Most spells still need a full action to cast and require their components anyway.
...Which is a moot point, since my PC group consists mostly of fighting/rogue types, with our only wizard being a barbarian multiclass who, thus far, prefers the sword to the spell, and a psionist/rogue who prefers using the variant psi rules from Monte's Psiscapes. I could kill for a traditional wizard in this party.
Perhaps I should explain my viewpoint... My conception of D&D-style wizards is inspired primarily by one of my favorite fictional wizards: Uncle, of Jackie Chan Adventures. He's a classic exemple of how such spellcasters can work. When he's actively casting a spell, he just points that Blowfish of his at the target and chants "Oomogweigwaifaimisaoh" over and over again as the spell does it's trick. But before he can do that, however, he always has to do "more research", spending a long time poring over his mystical tomes to find the magical formulae and gathering the ingrediants for the spell.
And that's exactly how I think Wizards should work, in my book: research the spell, prepare it ahead of time, then cast it as needed. The Wizard should always be the master of Prep Time spellcasting.
As for Spontaneous Spellcasting - Sorcerors don't prepare their spells ahead of time like Wizards, but instead spend 15 minutes concentrating to gather their mystic energies. They don't research their spells, but instead "Charge up their batteries" as it were. Bards also require a 15 minute concentration period consisting of singing, reciting or playing an instrument for that period.
To me, the Sorceror's preperation should have a completly different "feel" from the Wizard's, fitting the Sorceror's personal backstory/concept. Take your classic "dragon blooded" Sorceror. His meditation could consist of sitting in a drawn circle filled with his possessions and personal wealth, his "hoard" if you will, while uttering a mantra in Draconic as he meditates. A Sorceror with Demon Blood, on the other hand, could sit in a pentacle chanting the names of Demon Princes while invoking their power, etc...
This goes to the basic conceptual difference between the Wizard and the Sorceror: The Wizard's power lies in his mystic knowledge, while the Sorceror's power lies within his mind, body and/or soul..
The Quicken Spell metamagic feat's application is likewise unchanged, since all it does is reduce the Casting time to a free action. It doesn't affect Spell preperation, and as I've explained, I've kept the mechanics of spellcasting as they were.
Hope I've explained my position a bit better...