Shroomy
Adventurer
I think that multiclassing is going to get a lot better as more paragon paths are released. A lot of paragon paths boil down to "here's some abilities that focus you on a specific style of play or build option for this class." Which means that if you multiclass into that path, then take that paragon path, you've basically just received a bunch of level appropriate abilities from the class you were entering.
For example, look at the Kensei, or the Swordmaster. If you were intending to multiclass into Fighter, you could take one of these rather than spending extra feats to trade powers, and you'd get a bunch of neat Fighter-like abilities.
Even further than that, there is a HUGE amount of design space available for paragon paths that are, in and of themselves, what we would call multiclasses. The Wizard of the Spiral Tower is a great example. Suppose you're a wizard. You want to multiclass into Fighter because you want to attack with a sword as well as with spells. Well, you could do that, but you could also take a paragon path that's already been designed to give you exactly that outcome, customized to work well mechanically with the class you're already in.
That's the real power of the paragon path design system, in my opinion. Where 3e expected you to multiclass then used prestige classes to patch the mechanical flaws in your multiclass, 4e is set up in reverse- you can get the paragon path up front.
I suppose time will tell how well this design space is exploited, but it exists, they've dipped their fingers in, and I am hopeful.
Those are good points. I find that the 4e MC system to be one of the best parts of the game. On the surface, I think it looks deceptively simple and relatively gimped when compared to the freewheeling 3.x multi-classing, but its actually a multi-part system composed of the (1) initial multi-class feats, (2) power swap feats, (3) access to paragon paths, (4) the option of paragon multi-classing, and (5) access to class specific feats. There is a lot of potential flexibility in that core system and the fact that it is primarily feat based means you can bolt on extra sub-systems quite easily. I mean we've seen multi-class only classes, weapon specialization chains, feats that improve paragon multi-classing, and feats that give new powers to multi-class characters not available to the single-classed characters.