While I agree there's already some caster overlap wrt spells, I definitely would prefer--as others have stated--that each class be as mechanically distinct as possible. This was, in fact, one of my biggest issues with 4.0. The mechanical homogenization.
It's great to be able to switch from a rogue character to a wizard, and have them feel completely different. 3.5's problem was that not all of the mechanical systems were equally compelling. Building/playing a cleric was amazing. You had domain spells and powers to consider, whether or not to spend resources on martial prowess (and if so what kind of focus), and of course high level spells.
Meanwhile the poor fighter (and to a lesser extent the paladin and ranger) while different...was simplistic, fairly boring, and in some cases outright ineffective.
This new system pleases me, in that on a conceptual level it adds a lot of distinctive complexity to the fighter class.
It remains to be seen whether the paladin and/or ranger will be core classes or kits (as far as I know), but if they are core classes, it's my hope that they are given equally exciting toys.