You can often find a lot of parity in power choices from your main class to augment your ability with the other class. For example, poking around with the system, I made a 6th lvl Dwarf Wizard who multiclassed fighter, with the basic fighter multiclass feat and the Novice power swap feat (encounter power swap). As a wizard, he focuses on attack powers that work up close (any close spells, like burning hands), battlefield control (like web, freezing cloud), with a bit of range to open up. Utility wise he focuses on movement and defense (expeditious retreat, shield, dimension door) so he can remain mobile enough to compensate for his lack of armor. As a fighter, he focuses on solid damage and using his high con to his advantage by using a warhammer. He has crushing blow as an encounter power. I'm going to update him to 15th or so, with a fighter utility and daily, and try out the paragon multiclass option to really dive into the concept.
Personally, I love multiclassing. You control exactly how deep you go into the other class. My dwarf continues to gain wizard powers, even with the paragon option, only giving up a couple over his career in favor of fighter powers. I'm also working on a cleric/rogue, servant of a trickster god.
Oh, and you can safely ignore quantum, he doesn't get anything right at all in that post. It's just a nonsensical rant.