If you want to use windows 8 like a smartphone or tablet then probably yes to a touch screen. But you really do not have to use a touchscreen and can still use windows 8 like we do with win 7.
We will no doubt be able to toggle between Metro(tablet form) and windows 8 desktop form. In face we can turn of Metro completely with a slight registry tweek.
In essence win 8 is more like a win 7 upgrade with Metro thrown in. As I use a tablet a lot I will be interested to see how it will work in win 8 Pro. Note that MS is offered win 8 Pro for the same price....$40 But I want to know if I can save the download to a folder rather than simply using the 'Run" command. I have no idea yet if one can uninstall and then revert back to win 7.
There are numerous sites showing the two desktops for windows 8 and "how to's" from those using the beta copy. I wish I had a space computer to try it out as I would not want to download the release candidate/beta. The secret will be how to switch between the two. Also I understand that windows media player will be offered as a download so it may not be part of the win 8 package. Metro already have a lot of neat apps but no where near what apple offers for the iPad. For apps a touchscreen is best.
With win 8 if you already have win 7 then it should be a simple roll over in which you keep your old settings, programs and files. I will nevertheless make backup copies of my folders to my Seagate just in case. windows live mail may be a bit different but with more features I think.