I know we haven't gotten to wizards yet, but I want to throw this out there before I forget it.
I'm not a fan of all the new rules for spell casters with all the school powers, and unlimited 0 level spells, and bloodline powers, to name a few. I do like the ideas of them; just not how they are implemented presently, as they add too much complexity overall, and power creep in some instances.
I'd rather see much simpler rules overall, that plugs some of the obvious gaps in 3.5 without giving the PCs too much power (which is a problem I see as a DM with the beta rules, as the power level of the PCs makes too many monsters in the MM irrelevant far too quickly).
Hence the following idea. I'd like to see an ability like this:
Arcane Acumen A wizard gains Arcane Acumen at first level. She gains a number of spell slots equal to her Int modifier. These slots may be used to memorize spells equal to the highest level spell she can cast and may be split as the caster sees fit. For example, a 1st level wizard with a 15 intelligence gains 2 extra spell slots. As she can only cast 1st level spells, she may choose to memorize 2 additional 1st level spells. A 7th level wizard with 18 intelligence however would gain 4 extra spell slots. She may choose to memorize one additional 4th level spell, two 2nd level spells, four 1st level spells, or any combination thereof, adding up to 4 spell slots.
The purpose of this ability is to give low level wizards a boost, yet remain useful at higher levels, and provide some versatility to the rigid spell level progression chart.
A similar power can be given to the sorcerer, and perhaps the bard. I don't think clerics and druids need a power such as this.
I'm sorry, but do you really want to give high-level casters, (30 in a casting stat +) another 10 spots that can all be used on 9th level spells? That screams power creep like none other. I would say maybe keep it as a feat and have their casting stat be the number of extra spell levels that can be prepared, maybe for higher-level casters, changing it to score.
Arcane Acumen:
Prerequisites: Ability to cast arcane spells, spellcraft 1 rank.
A caster with this feat can prepare extra spell slots, or have an extra number of spells readied per day whose levels are equal or less than their casting stat modifier. For example, a sorcerer with 16 cha can have 3 spell levels worth of slots to use per day, split as he wishes (i.e. 3 1st level spells, or 1 3rd, or 1 1st and 1 2nd). Once the caster has spellcraft 10 ranks, that caster can instead prepare extra spell levels equal to 1/2 of the casting stat's score. For example, a wizard with 30 int can prepare 15 extra spell levels, divided as he wishes.
Special: This feat can be taken as a wizard bonus feat.
This version of the feat scales with level, and does not go really over kill for the high level casters (the 30 int caster now only gets 1 extra 9th level spell, as well as a few others).