In which way?
Mostly under the hood. There's a heck of a lot of work gone into bringing stability and compatibility to all the NG OSes. To a user, OS 4 probably seems much like OS 3 with bells and whistles, but to a coder they're leagues away from OS 3. This allows much faster porting and creation of programs which would not have been possible.
Then there's the ability to use hardware which we take for granted these days - USB 2, PCI Express, SATA, Gigabit ethernet, Gigabytes of RAM, Terabytes of hard disk space. All this has to be coded into the OS.
They are unique, but what are their unique selling point? From a hardware point of view, why do I want one of those instead of commodity hardware?
Because they're different.
Why does anyone want something that's different? It depends on the individual entirely.
For myself, I love my Sam 440ep because it's so fast, responsive and co-operative. It's a wonderful machine to code on.
I love my A1 G4 because it has more power and is fast enough to do most things, but it's still
fun.
I love my OS4 A4000 because it's the best of the Classic Amigas. It's 18 years old and can still run a modern browser. It's got
character.
How is that different from a linux? Actually, linux being open source I would think the user would be in charge on a level unparalleled by any closed source os.
It's different because Linux was never meant to be a desktop OS. There are more streamlined distros out there, but even so I've yet to see one that comes close to AmigaOS.
As a coder, I can do things quickly and easily that I just can't do with Linux. Linux is still mired in static library hell and incompatibilities and an obscure directory structure; AmigaOS is simple. It's pure. It's
fun.
I use Linux a lot - the Asus EEE PC I'm typing this on is running Linux - but I never code for it because it's horrible to code for. AmigaOS is a joy to code for.
But is it worth to bother taking the most out of hardware which is orders of magnitude less powerful than commodity hardware anyway?
Yes, most definitely. If we didn't, we'd all be using the same bog standard PC motherboard. A PC is just a PC, it's a bunch of chips shoved onto a motherboard in China that runs an OS.
An Amiga - be it an A4000, an AmigaOne X1000, a Sam, a Pegasos II, whatever - has
character. You can customise it, tweak it, develop it, enhance it, whatever you want, but most of all you can enjoy it.
That is why a Linux PC will never replace my Amigas. I have used both; I do not enjoy Linux. I do enjoy AmigaOS.