I actually first saw this in 3.5E, not in 4E, oddly enough.
It was when we started more carefully tracking the position of the characters, to deal with AoOs and so on. Then we saw something very similar - the "watcher-ish" player suddenly became very tactically adept and made very good use of their character, avoided and created opportunities for AoOs and did a good job generally, where the expert builder's character sort of blundered into the enemy and flailed at them.
However, as Mustrum says, I think this will actually make some players sad. One of my players is a long-time "power-gamer". He loves power-gaming dearly. He plays well, he's polite, he's funny, he RPs more than some of the others and advances the plot, but it's clear he gets big thrills from super-optimized characters and getting "phat l3wt". 3.5E was thus more or less perfect for him (even though his characters actually rarely stole the spotlight). He actually didn't get to play in the adventures I ran recently, but I suspect he'll be slightly LESS engaged than before, so this does cut both ways.
In 4E, though, I was PAINFULLY reminded of the tactical expertise of my brother. He DM'd 3.XE, so I'd forgotten about it. In 2E had frequently came up with terrifying plans or brilliant uses for spells. In 4E he played very smart and very tactical and spotted ALL SORTS of flaws in my plans, in and out of combat.
Overall? Seems like an improvement, but I hope there's enough chargen crunch to engage my power-gamer.