On the subject of spellcasting checks: Pretty much every other action in the game has a roll. Climb a wall? Climb check. Talk to someone? Diplomacy (or Persuade, as the case may be). Swing a sword? Attack roll. Know what's trying to eat you? Knowledge check. Cast a spell?... yeah, no problem, you've got this.
Eldan, you're talking about making sure that every spell does something even on a failed save. That means that every time you cast a spell, every time you attempt to rewrite reality with sheer willpower, you succeed. Every. Time. Why should it be easier to conjure a twenty-foot wall of iron then it is to climb a brick wall?
On the two roll subject... because you don't need DM feedback on the first one (the DCs are right there on your sheet), it's a pretty fast roll. Spellcasting-spell save is about the same amount of time as attack roll-damage roll. Maybe less. Especially since it spell resistance no longer involves its own roll. Damage spells will take a bit longer, but honestly, you don't play a blaster unless you like rolling fistfuls of d6s.
Perhaps there should be an option to take 10 on spellcasting checks out of combat, but I think that it's both a logical and balance point. Magic will always trump mundane by some margin in 3.5, and I don't think we can rewrite things enough to change that. And... well... think back to the last new player you saw pick up a caster. How many times did he/she say "Ok, I want to cast fireball. What do I roll?"
PairO'Dice, I do understand the Vancian prepared-spell-precasting flavor, but it's only applicable for prepared casters, which I'd almost prefer to leave out of the system altogether for balance reasons- there's a reason that all the T1 classes are prepared casters.
Eldan, additional replies:
*I WILL fill out more detail later, but that's a lot of work for things that are the same or almost the same as 3.5e. Right now I'm only updating during study breaks, so that's not really feasible. Besides, I'd like to get feedback on the big changes first.
*I'm not attached to the Concentration checks, although they're only made to eliminate penalties-- you can still cast if you fail the check.
EDIT: One more word on the subject of casting checks: Making it easier to cast low-level than high-level spells also helps make it less attractive to "go nova" and blow all your spell points on your highest-level spells.