Built-in voice commands at present aren't Nuance/Siri powered. I'm not sure what the difference will be in terms of the accuracy of recognition, but I for one have used some of the search functionality built into Dragon Go! and it understands me fine. I use voice dial, and can remember exactly one misdial in my ownership of the phone (from the car, no headset). All of that to say, I think it's a big misunderstanding to lump this in with current voice controls - maybe you didn't see the same presentation that I did. It was far more powerful.
That said, this is pretty much the 3GS all over again. Last year's design, new camera, speed bump, other guts upgrades, software features that won't be available to earlier models. Apple knows it can milk this design for another year with a modest spec bump behind Siri, so this was a smart business move. It's not the most compelling reason to upgrade, but the 3GS wasn't either, and I was really glad I did upgrade, especially whenever I picked up a 3G afterward.
I bet Apple will still be selling every one of these they can make for several weeks to come.
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