Apple used a version of NeXT, since Steve Jobs is a BIG part of the company. It was used because of UNIX's protected memory and true pre-emptive multitasking attributes. Apple has a developer subscription system. You pay $100 each year (not just students) and get the latest version of MPW (most people use Codewarrior, or, back in my day, Symantec C++ with it's excellent libraries), their standard compiler, as well as CD's with updated versions of the Inside Macintosh series. I have used damn near every application on the Mac, ESPECIALLY Photoshop, and have never had a stability problem with two applications. Example: I ran Photoshop, Premiere and Poser all at once one time for a project and had NO problems whatsoever.
On the Mac it's reversed browser-wise. IE sucks and Netscape works well (gee, isn't that surprising since IE runs on it's company's native OS for most people, and Netscape, the main competition, has problems. Do you think it would be hard for Bill to write an extra line of code to disrupt packet transmission in Netscape? Or double the ping?) I've never had a browser problem on Mac unless the site was corrupt. NEVER.
Setting the RAM allocation is a very good thing when you know a program is wasting all your memory. On Macintosh at least, Word did much better with the bare minimum of memory and so did the system, because Word no longer had free reign to spawn as many garbage processes as it liked. It had to deal with what you gave it. If you weren't skilled enough to know the proper amount of RAM, well then, your own damn fault. Personally I think screwing with the BIOS is the tool of the devil...there's too much opportunity for mistakes (and don't try and say doing that enforces stability, even the best have downed machines through BIOS manipulation). On Macs this isn't a problem because everything always works all the time end of story. No plug and pray, just go go go.