I've tried to connect to Windows 8 Developer Preview via rdesktop 1.6 and freerdp 0.8.2 from linux and there was no success.
I've get:
ui_unimpl: NOT IMPLEMENTED: Unknown Capability Set 0x1E ui_unimpl: NOT IMPLEMENTED: Bpp 254
Although I could set a connection from Windows 7. What is the version of RDP on Windows 8? Is there any rdp client on linux that supports such version?
RDP underwent significant work in Windows 8 and likely does not yet have any support from non-Microsoft maintained clients. Remoting from Windows 7 should work properly. Some capabilities that were added in Windows 7 may now be taken advantage of which is why Windows 7 to Windows 8 may work while Linux to Windows 8 may not. That is to say, Windows 7's RDP client already supported the new capabilities.