I got an AmigaOne, and I love it. Of course, I'm one of the lucky few with OS4 on mine, but really I'm very glad I bought it.
OS4 is really nice, even in its beta state. At first I was skeptical about some of the new features, like the idea of libraries having a new interface scheme, but now i've got it on my desktop and had a chance to try it out, it really kicks ass!
I've used MorphOS a couple of times, and it seems very nice, but IMHO its no substitute for the real thing ;-).
If you're on the fence, why not wait until OS4 is out and try them both before you buy.