For now vArranger can play Ketron styles (not audya), Yamaha styles, including Tyros 4.
Roland styles will come then
Korg styles after. (someone knows a little bit about the compression algorythm used by korg?)

Dnj, I don't think software arrangers will take place over the hardware arrangers, but in some situations they are very useful.

I know that I have on my toolbox a working vArranger inside my laptop, and when I need it, I just have to plug any midi keyboard, my Ketron SD2, and voila.