Love it.
Its very different from 3e multiclassing. But its a better solution.
A 3e multiclass character often fell far from both trees. For example, if you played a multiclass 50/50 fighter/wizard, and you ever tried to rely on straight melee with no magical buffs, you were a fool. You lacked the HP, attack bonus, and AC to accomplish that. Likewise, if you tried to rely on throwing fireballs at someone, you were (less, but still) a fool. Your best bet was to create a hybrid buff/power attack/polymorph combination that resembled none of the original classes. Or, run as fast as you could for a PRC.
Now, we don't have full 50/50s. But we DO have a structure that lets a Fighter/Wizard cast a Fireball and expect it to rock someone's world. That fireball is no longer massively gimped by coming from a multiclass character. Likewise, a Wizard/Fighter who wants to bust someone's head with an ax can take a Fighter power that lets him do that, and gains a great backup for when things get dirty and close quarters.
Meanwhile, the 50/50s sucked before until you got a PRC to fix them. Now they'll need base classes. Its not that different, but it does have a "we meant to do it this way" vibe that 3e multiclass PRCs did not. I'm ok with that. We've already got one (in spite of what people pretend, paladin is a cleric/fighter hybrid, always has been). The spellblade or whatever the heck its called is coming out rather soon for those who want magical buffs and teleports to augment their melee.