I don't come from an Amiga background (But rather C64 "OS", MacOS and MSDOS was my primary systems as a kid) - and apparently all this thing that's so amazing and awesome with AmigaOS flies totally over my head.
However I bought both an Pegasos back in 2003/2004- the first system outside Amigas that run MorphOS- I also purchased a license for one of my G5s (Mostly out of support for the people that spent an lot of time to develop it, although I must say I've become quite disappointed in the G5 port considering an update totally broke the SATA bus for me- the G5 doesn't detect anything but the CD/DVD drive nowdays thus is unusable on the G5 on anything newer than the last release that actually worked on it)...
If you expect MorphOS to be something special, something that Mac OS X or MacOS 9 is not- you will be disappointed, the system is in some aspects worse than Mac OS 9- what it has that Mac OS 9 never really had good support for is preemptive multitasking, but that's basically it- outside the fact that the developers did write or port quite a lot of software that makes it somewhat useful if you can live with a system with worse memory management than MSDOS- but for example the OWB browser is a relatively modern Webkit based browser that at least the last time I tried it was quite fast considering the hardware. Other than that it's not much to write home about unless it ticks your Amiga nostalgy synapse- the community is among the worst I ever encountered, while there are some people that are very nice and helpful the vast majority are extremely hostile- too be honest even the simplest question often ends up getting answers similar to what Linus Torvalds (renowned for his terrible argumentation techniques and lack of social skills).
When it comes to productivity software, unless there is some well known open source program that has been ported- you can forget about it, if you're lucky you may find something from the 90s that still works (MorphOS does not emulate the Amiga chipset however, so unless it's a well written (read using only the public APIs) application it just won't work- forget about 99% of all Amiga games, if there is some halfassed productivity software somehow still in development (like for example a decent text editor with chroma coloring support) expect the pricetag to be outrageous.
As for the open source software- it's more of a novelity than something useful, Linux runs it all better and more stable.
If you're interested in retro amiga stuff, better get an amiga emulator.
Sorry if this sounds negative, but I'm trying to be honest about my feelings about it- I did spend over $1500 on MorphOS and related hardware, it's fun to have but was it worth it? No not at all.
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Better clarify,
Did the developers behind MorphOS do something incredible? Yes absolutely they did. And some of them are extremely kind people too (others are complete arses however).
But is it a practical system that breaths new life into your aging hardware? No it's not, it brings features AmigaOS had back in the late 90s- no much happened since.
I'm not trying to say it's a bad system, I'm mainly trying to highlight the only reason people rave about it is because they are Amiga heads- and the Macintosh community would probably claim a thirdparty rewrite of Mac OS 9 would be the best, most ingenious OS ever created as well if it was released today.
But as it's available as a timelimited demo (I think you can run it for 30 minutes at a time- before it essentially crashes) if your Mac supports it, go for it- try it out.