At Proaudiostar.com, they have a B-Stock unit for $469, and when I asked them about this, they said that it was no longer available, but they would honor that price for a brand new unit.
For those interested, that B-Stock item is still "available."
I own the Casio PX-330 - I never used the arranger part of it, and I never played around with the non-piano instruments. From the demos, it seems like the piano voice in the PX-150 is much richer.
For those who are interested, the keybed and the piano samples on the PX-150 are the same as the PX-350, 750, and 850. The major differences between these models are speaker size, additional voices, and what inputs and outputs they have.
I'll review the board when I get it.