I thinking of upgrading an XP box I have to 8.  This is a desktop bought (2 years ago) as a 'barebones' PC that I installed an existing copy of XP on - so the hardware is considerably more modern than XP is.  This box is used as a file server first and a PC for a user that needs an email client and browser for non-games purposes.

The main motivation for doing this is curiosity about Win 8, followed by an acceptance that XP is fairly dated now.  This is the only XP box I have - the other 2 are Win 7.  It is my understanding that for a limited time Win 8 pro can be downloaded to up to 5 PCs for $NZ49.95 from MS.  This is by far the cheapest Windows upgrade offer I can remember.

My understanding is that each Windows release performs best if Windows is re-installed from scratch (meaning that a new registry is created and all applications need to be installed again).  Are there install options with Win 8 that deliver the performance benefit of an initialised registry without the need to reinstall applications?

I am aware the Win 8 has a new desktop interface and I intend to try it out - but my hardware does not include a touch screen.  I am aware of a number of options to get a Win 7 style start bar if needed.

Are there any other pitfalls I should be aware of?