TBH OS4 has come a long way regarding the visual aspect, especially compared to 7 years before or so. I don't know for example, why MorphOS comes with folders as icons instead of drawers since for every (returning) user, this is an alien concept. I had to replace most of them from tommysammy's excellent icon packs and I hope he makes some packs especially geared for MorphOS. Also, OS4 theme looks better at least to my eyes and more "amigish". Add a blue backdrop and you are set to go. Regarding the centralized (and organized) options menu I prefer it to the old one from 3.x that has continued to 4.x as well. Other than these, I am pretty sure that if you put "AmigaOS" instead of MorphOS on the screenbar, most people will have trouble identifying which OS they will be using (not in terms of functionality but as a first glance for its look and feel). I am also interested to know what other users are missing from OS4 (or even OS3) compared to MorphOS.
