I just bought me my first Mac... a Mac Mini. It's a lovely machine. It wipes the floor with PCs. It's small, cheap, very very quiet, comes with good software and runs a nice OS.... what more can you ask for?
However, it's not an Amiga. There will never be a real (i.e. modern) AmigaOS for it because there's no money in relying on commercial host O/Ses... look at BeOS for example. You need to run on dedicated hardware or people will use the hardware for the OS that's meant for it. That's why there's no x86 AmigaOS - everyone would just use Windoze because there's more software for it. Necessity is the mother of invention. Take away the necessity of writing software for the hosted OS, and you get no invention.
MacOS is very nice now, but it's not perfect. It has lovely features (love pressing F9!

) and it looks very nice, and it's fast.. but it's a memory hog (1/2Gig minimum), it's a little clunky at times (though only usually when you're out of RAM to be fair), at least compared to AmigaOS. It's a little gargantuan (it's a UNIX system after all). In terms of lean design the AmigaOS wins hands down. In terms of features, the Mac does.
I'd recommend getting a Mac to replace the PC, but not the Amiga... there's still not quite the same element of
fun in it somehow! (And don't even begin to think that running UAE on a Mac will replace a modern Amiga - it won't. It just runs a 10-year-old version of AmigaOS a bit slowly. Run an AmigaOne with AmigaOS4 and you'll see what I mean).