Please see my solution here.
I just upgraded my L702x to Windows 8 and everything is working well with the out of box or Windows 7 drivers however I noticed that Dell has listed all the Windows 8 compatible updates on the Drivers and Downloads page for the L702x so I thought I would download and install them.  Well, over 24 hours later, any attempt to download the updated files only results in an error. For the single file downloads, I get the error:  Sorry, the requested file could not be downloaded For attempts using Dell Download Manager, I get a big red X and:  File not found  Seriously? How come we have to go through this every time Dell posts updates to the website? You would think they would have planned a high demand for the files on or just after the Windows 8 public release and not list the files as "available" on the website if they aren't actually on the server ready to download.   Way to go!   
XPS17 L702x Windows 8 Drivers