I sometimes wonder if you pared down the spell lists somewhat and then let casters cast spontaneously, if it would be better.
My RPG uses a "build spells on the fly" style, and there's really no such thing as "memorizing spells" unless you limit yourself purposefully (which is doable mechanically). It definitely opens things up, and I like it a lot more. If spells are balanced*, I think it can open things up a lot, and add a lot of fun to spellcasting. As always, play what you like
* [WARNING: RAMBLING AHEAD] Yes, opinions differ on "balance". Since this method adds a lot of versatility to magicians, I "balanced" it by making them do less damage unless they spent a lot of resources, toning down the power of spells (things like invisibility give concealment, but you need to make Hide checks like normal), and drastically slowed down spell regeneration (a single level 5 spell slot takes 2 days to come back, for example, and spells don't overlap. That is, if you use two level 5 spell slots, that's 4 days before it's all back).
Again, I balanced the slower regeneration time with the ability to cast spells at will, albeit not as efficiently. So, at low level, you can basically cast low level 1 spells at will, while at level 16 you might be able to cast level 3's or 4's without difficulty. Then, when you want to kick some ass, you spend your level 8 spell slot (16 days to get back), and do your best to help out (the system really does reward helping allies over hurting enemies, which I've put much thought into). This preserves resource management, but enables a constant stream of spells that your magician can use, and varied in use at that.
This makes magicians kind of a "jack of all trades, master of none" unless they buy the Specialization or Lost version of certain "threads" (basically schools of magic, of which there are 20). Having the Lost Elemental thread might let them deal nearly 70 damage (on average) as a level 8 spell, but it's a short burst of damage on a high recharge time (16 days). It also takes heavy investment to get that high (you need the Specialization and Lost version of Elemental), and you have to be level 15 to get your first level 8 spell slot (well, most of the time, at least).
As far as single attacks go, 70 damage is a lot, but the damage-focused warrior builds will probably be doing 58 damage per round (unless they're getting extra attacks, which will put them at 87-116) with no resources consumed. Of course, that damage will come at a high cost (since the game is point-buy), so the damage-focused warrior builds will be much better at damage, and not nearly as broad as a skill-based build (which might be something close to Batman... think Nightwing

). So while a damage-focused magician might get one round of rivaling a damage-focused warrior build, he consumes massive resources to accomplish it (16 days before he can do that again), but this is complemented by his vast amount of versatility (he can cast a useful spell in almost any situation, even if it means making someone else better), and has an endless supply of at-will spells he can cast that become more powerful as he levels.
But, enough on this. I just meant to say (I think I need to put a warning at the top of this...) is that I think Hussar is correct . At least, as far as my players go (since my game has no "spell list", though the options are compounded, which probably goes against what Hussar means...). Of course, fun varies. As always, play what you like
