it is not only on handhelt devices where a touchscreen makes some sense , it works in museums and some shows too , but for at home on a computer , i dont think it makes any sense
but indeed i agree all the features in lion that come from iOS and some new features in iLife 11 would work with a touchscreen iMac out of the box , but i guess that's what the magic trackpad is meant for
and like so many i think touchscreens work on small screens better ,
so the max size where it makes a bit of sense would be the iMac 21.5 and maybe on the MacBook 's , just because thats the screen sizes other pc makers offer touchscreens for , but even there the use is restricted ,sure you could open itunes and select your favorite song with a touchscreen or look through your iphoto collection , maybe even read a book by turning over the pages on the display ....
but as i not even like the glossy glass in front of the iMac display , imagine how horrible that looks with hundreds of fingerprints on , you then spend more time with cleaning then using the iMac
...and whats so wrong about having to use a mouse nowadays or the magic trackpad for that matter
aaah .. i know it what thats all about , with a touchscreen the iMac could possibly become cheaper, as apple could deliver it without keyboard and mouse as you certainly have no use for a keyboard and mouse if you got a touchscreen or ?
having said all the above, i heard that you can actually use a iPad to fully control a iMac , means you can replace your keyboard and mouse and if you got a trackpad you can replace that too, all with just one device ...the iPad ..somehow it seems i just found something the iPad could be of real use for ...ok a quiet expensive keyboard and mouse/trackpad , but it seems to work and there it is your external touchscreen for the iMac... hey apple what about a cheaper version of the iPad that only functions as bluetooth keyboard and mouse/ trackpad ...i offer £200 for that then