i have the supposed F series phone that you mentioned. It is true that these new revisions have slightly different versions with different materials. The build of my phone is pretty much what this thread describes it as, purple(albeit very slight) frame and gritty keyboard.
http://forum.ppcgeeks.com/showthread...ghlight=purple
it probably is not worth upgrading to this newest version unless you really hate the feel of your keyboard as the hardware itself is not upgraded.