I agree, -Avalon-, and I love that spells that were only useable for a few levels in 3.x will now get play for 30. Its one of the things I love about 4e.
However, I also think a spell that a caster can only fire off once a day at level 3 should be useable at least a couple times a day by a 28th level caster. So, maybe a daily can be made into an encounter or an at-will spell at higher levels, (which would be great).
I also remember hearing something about abilities that will allow higher level characters to recharge daily powers--so maybe higher level wizards can just take an ability and fire off their dailies 2 or 3 times a day?
One thing I loved about 3.x spell casting was the way, over time, a character could prepare x number of spells of each level--which at higher levels, meant a slinger could have Meteor Swarm, Imprisonment, Crushing Hand and Time Stop all ready to go--or he or she could have 4 Meteor Swarms on deck. I'm just hoping that casters will still have some of that flexibility in 4e.