I just bought a brand new 15" and did not order the SSD from Apple, but a separate one from Intel.
It was not to save money - in fact, the price is almost exactly the same and I just get 160GB instead of 256GB.
The reason was for getting a high-performance SSD for a high-performance Macbook Pro (supposedly).
Apple's SSD:s seems to be geared towards high capacity instead of high performance, which is my experience from the Macbook Air - thus I ordered an Intel X-25 instead.
They are almost exactly the same price as Apples (650 USD).
So please stop making the assumption that no one would buy an SSD separately and being concerned about performance - that is in fact the only way to get a high-performance SSD drive into the Macbook Pro - Apple does not sell one.
Thus, the question whether we can access the 270MB/s read speed from these beasts, is a real question.
I'll see what happens on monday when the Macbook Pro is delivered, the SSD is waiting...