Well, I've been checking out reviews of it and they seem to be all positive. That said, taking a look at it myself, it doesn't seem like anything that special to me. It seems more like something a hobbyist would pick up to self-teach how to play a piano, rather than something a musician would use to make music with when he has a MIDI keyboard already. However this is just at face value; I haven't taken a good look at it yet and I'm not even very knowledgeable in portable keyboards (all I really care about is MIDI support). Yamaha's a great brand and I haven't tried the keyboard myself so for all I know it could be amazing.
Why exactly do you plan on getting it? What features does it have that lured you in when you already have a MIDI keyboard? If you want it for its sounds, I personally think a better idea is to invest in some good VSTs/sound libraries to use your MIDI keyboard with, rather than buying a new keyboard entirely. If you want it to be able to make music with it without needing a computer, then you can go for it I guess, although again, it seems more like something a hobbyist rather than a musician would use for something like that.
This is just my honest opinion though. Someone who's more qualified than me should give you a clearer and more accurate overview, since I'm no expert!