Hi. I got one about a month ago. It's the same basic board as the other Casio Privia's but with more features, sounds, etc. Don't expect too much from the other sounds. I like it, and at a bargain price (about $500 here in Japan) the only thing close was the Yamaha P-60. The P-60 is reputed to have a better piano feel and piano sound if that is the most important thing to you. But, it has few other features.
Bad news: the pX-400r does not have a usb driver for Mac.