I whole heartedly have to agree diversity and choice is the key. The Amiga's merits (and it's children/variants) have always come from it's unique features.
However points should be made and folks I own Macs, PCs, and Amigas.. Hell I even have ran AROS on x86 from time to time..
Everyone knows that MacOS X is really a flavor of Unix underneath just like Linux is a flavor of unix, and runs on different cpus..
The truth of the matter is the Amiga is not unique anymore for it's multi-tasking, graphics, etc. Through Linux, OS X, and yes even Windows XP, the world now has multi-tasking operating systems and great graphics.
There is nothing special now about the Amiga except it's unique library of software (most of which you can't get anymore unless you are pirating software from company's that aren't around anymore)..
The Amiga was my 4th computer ever, however it was the one I most loved, it brought me into the world of painting, animation, and later desktop video production. I will always love it for what it is. I just think it was a great idea, that has been very copied by everyone and I love the OS for what it is.
Who cares if the G4 is slower than intel machines (Apple doesn't seem to care) because the Mac platform is more than the sum of it's parts, and to that effect so is the Amiga.
The Amiga community is full of very astute smart people who are very supportive and friendly. The community is the best thing the Amiga has going for it.