>Just wondering if anyone here had any experience upgrading from 6.0 to 8.0. If yes, how smooth was the transition?

YMMV. Before you start, check What's New in Visual FoxPro section of the help, in particular Behavior Changes Since ..." :
What's New in Visual FoxPro 7.0 http://msdn.microsoft.com/library/default.asp?url=/library/en-us/fox7help/html/newwhats_new_in_visual_foxpro60.asp
What's New in Visual FoxPro 8.0 http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dv_foxhelp/html/fooriwhatsnewinvisualfoxpro80.asp