Since I have the Kemper I feel the difference in sound quality much more than before.
Same here, Harry.
Through my old POD HD500 it kinda sounded like the shite (good). The second I plugged into the Kemper, not so much; suddenly I needed a real guitar.
That said, I still think the acoustic sims are great, and plan to use them in-the-mix for rock / pop stuff. I wouldn't dare use them solo, so I'll have to make sure I don't write anything for solo acoustic guitar as I don't have a "real" one.