Macs currently run a UNIX derivative called OSX. The current version is often refered to as Jaguare or Jawyre, it is considered to be the first TRUE version of OSX. It's totaly stable (has crashed on me once in the entire year I owned it, and I caused the crash thrugh some bad programming).

OSX has several "layers", the largest most important component of the OS is Darwin. This is the core layer of the OS, it is based off of BSD UNIX and is fully open source (there is even an x86 version). Because of Darwin a huge amount of open source software has been ported over to OSX, including X11. This allowes one to run alternate desktops environments like KDE and GNOME right over Aqua/Quartz seemlessly.

Aqua/Quartz is the next major layer. This is the eye candy of OSX, Aqua is the UI name, Quartz is the powerful rendering engine that powers Aqua. Quartz employes OpenGL and graphics acceleration to produce one of the most well designed and good looking GUI's. Simply put, OSX is beutifull. On a powerfull computer (400Mhz+) with plenty of Ram (Id say anything above 128MB is great), it run's seemlessly without a hitch. RAM is the key to OSX (if you decide to run Aqua), it hogs RAM like a bitch, but when you got enugh it manages it perfectly so you can't really complain.

Folks often complain that OSX is not true open source because the GUI is not open source. If this is a problem, download Darwin and install X11 and KDE if you want. None the less, Aqua/Quartz is incredibly pourus and easely customizable, nearly all aspects of the GUI are in reach. as sites like www.resexcellence.com are testament to. While the GUI bears the trademark Apple quality as far as desgin and ease of use that even a first time computer user could get used to, the UNIX core is never out of reach. Just boot up a terminal window and your in darwin. At startup you can type >cosole as your username and you enter full darwin mode. There are several otherways of bypassing Aqua into Darwin.

As mentioned before, project's like Fink amongst others are porting Open source software left and right, but aside from the software form the Linux/*NIX world which is rapidly coming to OSX, there are plenty of OSX only Open source and freeware stuff coming out all the time!

This is largely due to the fact that OSX comes with a wonderfull suite of free development tools from the gcc compilers, to apples spectacular Developer Tools. Objective C (OSX's prefered language for creating COCO applications) is incredibly easy to use and learn.

COCO, Carbon, and Classic are words you will hear often. Because the MacOS was not allways UNIX, apple preserved many of the origional API's in OSX's API's. These API's manifest themselves in a Carbon and Classic set. Classic API's are only related to the older Mac OS and programs that use them must be run under classic emulation within OSX (Rather seemlessly implimented BTW), Carbon programms are those that have been modified to use the Carbon API calls, these API's are virtually identical to the Classic API's but are "translated" internaly into OSX API's. This makes Carbon and Classic programms run a bit slower than they could (not usually a noticable speed hit). COCO is the incredibly fast OSX only API's. I am currently typeing in Chimera, a fully COCO OSX implementation of Mozilla's Gecko engine. It is the fastest browser in the universe .

Mac's aren't hard to upgrade at all. Processor upgrades, vidCards and all maner of other hardware exist (perhapse not as many choices as the PC world) but MORE than enugh. Now, if you get an iMac or one of the other all in one unit's upgrading can be a pain. But all the towers etc. are fine. This is a huge Mac myth.

Also, Mac's are long lived. You will keep a Mac far more than 3 years, and it will be fully usable .

Let's see what elese...

Oh, you can run Linux on a Mac. You can dual boot with YDL, Mandrake, Debian, amongs't other popular distros. Right now my comp has 4 OS's. YDL, OSX, OS9, and Win98SE. Win98SE? Yes, I run VPC to play old DOS abandonware:-).

One more thing about Mac's, they have a plethora of main stream Apps and Games which Linux lacks. You have the choice of running GIMP or Photoshop on OSX, as well as M$ Office or OpenOffice.

IMHO, Mac's are excelent computers! I would never switch to PC.