OSX sucks because of the heavy use of eye candy on an slow g4 chip(s) on a half assed motherboard design. All those benchmarks they quote are crap.. the fastest dual G4 is alot slower then the top of the line p4/athlon doing just about anything. To be honest I like classic macos 7.6x to 9.1 in some respects (like not having a registry and being able to move directories to different drives and still being able to run the app and not having to reinstall the os 2 times a year) Though memory management sucked, stability could be better, and multitasking wasnt too hot.
Linux sucks because there are too many distro's that try very hard to be WINDOWS with all its bloatware. I ran an older version of mandrake that did auto updates from the web. I did a clean install, ran update, rebooted, and then had a non functional computer (nice self destruct feature!). There are very few everydy apps for linux, and just about no games. So unless you run a very busy server why bother? I dont want to have to modify an app to get it to work with my version of linux. The directory structure is a mess. Most of the programs look like some kid almost out of college slapped it together for a school project and left it 80% finished. Redhat and mandrake own the linux distribution mass market and both are buggy as hell.
BEOS never got going as far as I am concerned.
QNX never looked like it was anything other then an embedded OS (which is what people use it for).
One of these days M$ will make a completely new version of an OS that isnt compatible with windows at all (might even be a distant relative of unix) but will have a native version of office, media player, directx support, explorer and will sell like hotcakes.