If you wish to start with Windows8 only then wait for a while, else you can purchase the machine now with Windows7 and later on upgrade it with Windows8.
Undoubtedly, using Win8 would be the marvelous experience, last week I went out in market on electronic store there I hands on the trial version of Windows8 and man believe me it was outstanding!
interface was way better than any of the Windows launched ever!
I am planning on getting a high-end Desktop for personal use, with a 25" non-touch flat screen. (e.g. HP8 or 9)
Am I better off buying now and getting Windows-7, or waiting for Windows-8 and using in non-touch mode?