I started out with an Altair back in the late '70's -- before IBM ever thought about making a PC. Used MS-DOS from v1.0 through 5.0. Never liked windows in the early DOS days, OS/2 version 2 had promise but no apps. I ran USL System V r4.2 for ages and really liked it, played with Linux off and on since the days when it would fit on a single floppy. Currently my 3 computers have XP Pro, CentOS 5, and Vista
In my opinion, for a desktop OS, 64-bit Vista Ultimate kicks everything else's butt.
XP is OK, (I support hundreds of XP boxes) but you have to make the user a local administrator for them to get anything done, and at that point XP doesn't do anything to prevent programs from whacking the registry or scribbling all over the system files. I keep a thumb-drive on a string around my neck that just has programs to fix broken registry entries, re-register the default DLLs, and set the permissions on the registry and OS folders back to what they should be. None of those things should ever have to be done, but I use it 3-5 times a week. Programs misbehave, and XP lets them. You don't have to give a Vista user admin rights, and even if you do, it'll still whack a misbehaving program.
I hear two types of people criticizing Vista. Most of them are people who never ran it and just like to repeat the vague warnings they heard from other people who've never run it. The few others are people who complain about it not running their favorite program -- "It ran on XP!" -- well, I've looked at about a dozen of those, and so far it's always been XP's bad. every one of those programs was doing something it shouldn't (retarded stuff like installing user data files data files into system directories) XP was too dumb to catch it; Vista wasn't
I used to like Linux years ago, but the distributions have all gotten flakey. They install apps all over the place with no rhyme or reason and you've got to go on a scavenger hunt and get bits and pieces of junk from all over the web to get anything to run. I have it running here at home just to mess with because I have to support it at work. They've all got their little 'magic' updaters like 'yum' or 'apt-get' that are supposed to do all the hunting and fetching for you, but they just give developers an excuse for being even more sloppy. It's lame.
If you don't have any commercial apps you need to run, Solaris is a pretty good free Unix. FreeBSD runs on smaller boxes, but I've always preferred System V -- maybe just prejudice. Solaris has a better-optimized compilation system and more sophisticated development tools than FreeBSD. My favorite server OS of all time was OSF/1. It was slick and fast and the compiler would switch from BSD mode or SysV mode with a single command line switch. I liked AIX's too It's CSet2's linker would do stuff with shared objects nothing else could do.
Paying money for Unix is a thing of the past though . . . .
I don't have much experience with Macs. My boss has one. I've played with it and a few others. They seem to work OK, but I don't see what the big deal is -- I suspect it's mostly a fashion statement, but I really don't know. The ability to use mainstream commercial apps and build Unix/X11 apps on the same box has some appeal. I guess if you could get used to the Mac's oddball GUI it might be OK. I don't see myself ever spending my money on one, though.
At some point you've gotta stop dinking with the tools and start using them to do some work, right?