Ok, sorry about my rambling... but here I go again.
I think (now, after reading this thread) they should just scratch this Rage Strike altogether.
I got 3 reasons.
1) Unnecessary: there's really no need for this feature to be there. You could simply make an exception to the "Effect" clause on the barb's dailies to allow you whether activating another daily would change your current rage state. This way you'd use another Rage Attack and decide whether you want or not to be under the effects of the second Rage, or keep the first one.
On the same note, they (the designers) should focus on encouraging you to spend your dailies throughout the encounters, and not all of them in the same one. Barbarians got plenty of stuff that gets better when you're raging, which means, they'd work better if you spend them between encounters.
2) Confusing: many people won't understand the feature. Many here didn't. I keep hearing that 4E simplificates the game, where in fact I had no real problem with 3.X when it came to rules, honestly. But if you claim that your new system is gonna simplificate things, you gotta stand up for it. I had a really hard time explaining my players stuff like Healing Surges vs. Second Wind, Bursts vs. Blasts, even milestones, Warlocks/Rangers contraditory mechanics (Prime Shot vs. Mark/Quarry). The barbarian has lots of stuff like that that's overcomplicated for no reason.
3) Misleading: Rage Strike looks like one thing, where it isn't. It looks like a "neat" feature that adds more power to you, or at that least that's what it seems when you read "at-will" written on it, where in fact it's just a tool to fix a problem... that IMO doesn't even exist.