AmigaOS - Commercial operating system, currently coming up to version 4.0 (full release). Not open source, unless of course its AROS which is similar to AmigaOS 3.x but runs on x86 hardware.
Advantages of AmigaOS - There are some good games for it, fun to play around with since it is quite hard to mess up AmigaOS.
Disadvantages of AmigaOS - As far as modern applications go, it is quite weak. Although this is no fault of the operating system itself in most cases, this is just the small market and shortage of developers. Another thing to bare in mind is that although AmigaOS may be behind in features and standards compared to a lot of other OS's out there, AmigaOS has had many different owners and thus has caused a big gap in development, causing the current developers, Hyperion, to work extremely hard trying to "catch up" to the other features of its rivals.
Despite this being a massive job, it is not neccesarily impossible, and from what users of OS 4 have said, it is already a big improvement over the previous AmigaOS release, which was 3.9 in 2000.
