There is simply not enough useful software available for AmigaOS. Sure, I can surf the net (kind of) in Ibrowse and send e-mails with YAM, and customise my OS look until the cows come home, but what else is there?
I guess it depends on what you consider "useful software". I personally have WAY more useful Amiga software than I ever had when I had a Windows computer. Probably the main reason for this is that almost all Amiga software is neatly arranged on Aminet and Windows software is scattered over millions of sites and you have to sift through the crap (and get infected with spyware). And if you want professional Windows software, it's damn expensive.
Besides the IBrowse and YAM and customizing until the cows (..and sheep) come home, I do lots of other stuff. (graphics, music, fax, create PDFs, spreadsheets, databases, slideshows, astronomy)
Edit: x56h34 - I reread your original post and saw that when you said there was not enough useful software you were referring to AOS4/MOS. In that case, I totally agree with you.