With some applications you notice the emulation more than others. The applications may not be as responsive when you first open them. For the person that bought the Intel-based Mac and is looking for that performance increase, the bigger bang will come from the native code.
It's the psychological barrier. There are people who might be interested in a Mac who wouldn't have bought one because they're afraid they might need Windows.
I'd be shocked if we saw a scenario where a bunch of people went out, bought Macs, and only ran Windows on them.