W8 has better multi-core management. Increased speed.
The only real reason to not go w8 is lack of stable drivers for your existing audio card.
Once a computer is properly configured for its intended use, and user, all the drool about lack of start menu, and 8 is only for touch, is revealed to be just C R A P.
I think the Start-menu-metro-shortcut-wall is way stoopid. My music computer displays nearly 90 shortcuts. This is just plain dumb. I prefer a well organized hierarchical menu.
So, on the desktop is a shortcut to open the windows explorer to display the actual start menu folder. Just like the old days.
I support about 40 computers (xp, vista, 7 and 8) for a dozen small businesses and home users. Most users/owners never attempted to configure the old start menu, or deleted all the factory debris on the desktop, or remove all the showroom stickers.
Very few of my clients ever need to use the start menu: new or old. I configure the desktop, and taskbar to contain links to most all the tasks they perform, I add utilities (PDF reader,...) and default programs to use the correct (desktop) versions of these tools.
It takes me 6-8 hours to setup a new computer. This includes creating the factory restore disks, updating the OS, installation and updating of additional programs (office, FF, Thunderbird), transfer of data, configuring UI for intended use, disk cleaning and disk imaging. Onsite: install printers, network, internet access, shared folders, and data transfer,...
Got updated audio device drivers? Get w8. Drivers never gonna be updated? Get a new interface, and w8.