Is it right that there are seperate mechanics for at-will and vancian casting? If so, that puts up a flag for me - there should ideally be no "you can cast a spell this way by memorizing but you use it once and it's spent OR this way with a feat only with the feat you can do it all day blah blah blah"....it should perhaps be "spells are cast this way". That's the only way to make it as approachable as past editions.