That's the problem isn't it "anyone who's ever used an Amiga". It's the same attitude that keeps Linux from being usable by anyone on the desktop, the developers and existing user are all used too it's fault and "know" what they need to do already.
New users are scorned and told to read the forums etc. It takes someone techy enough to get past all of that and start using it, by the time you've done so, you're one of those who already knows what extras you need.
In essence what you are saying is that for any new OS to be successful its gotta be more or less the same of what people have been using. Fine then, stick to winblows. Why would that user want to change to a different OS if all they want is the same as what they are used to? They wouldn't. The target market for a AmigOS is not people who have never used Amiga before, its ex-Amigans. And there are lots of those. All would know what "snapshot" and DOpus mean.
With Linux its not just a case of "its different, so thats what's stopping it from being used on the desktop. The major problem with it has been not that its different, its that it requires a familiarity with the CLI. That requires a good familiarity with the file and directory structure as well as user heirarchies. This is not the same thing as pulling down a menu with an item "snapshot" in it and trying it out to see what it does. Done once its never forgotten, unlike CLI commands and switches. Or double clicking on an icon that says "DOpus file manager", with a buttons that say "drives", "copy", "move", "delete", "unarchive", "play", "show" etc, etc.
If i had a decent browser, and media support, pdf support most of what I use my Windows PC for would be covered.