What Mac users tend to forget is that there is no such thing as a "Mac" anymore.
Since the very first Mac, Apple has slowly brought their computers more towards the standard technology of PCs. PCI instead of NuBus, USB instead of Firewire, IDE instead of the proprietary form of SCSI that they used. The one thing that set Macs apart from PCs was their processors.
In 2006, Apple switched their processors from PowerPCs to Intel processors, removing the last ounce of difference between Mac hardware and PC hardware. I have heard some Mac users proclaim that this is not the case; that Macs use EFI and PCs use a legacy BIOS. While this is true in general, one can purchase motherboards that use EFI if they so desire. And when Vista's Service Pack 1 comes out, it will fully support EFI as well. Once Vista does, more PC manufacturers will ship their computers with EFI.
Now for the software, and the things that I have heard about it. Most of what I hear is as follows:
1. Macs never crash.
2. Macs are easy to use
3. Mac OS X is optimized for the processor they run on.
1. All operating systems and all programs have the ability to crash. Even the slightest flaw in a piece of software or hardware can bring a system down. Windows crashes, Linux crashes, Mac OS X crashes. Even QNX, a real-time operating system used in embedded devices and designed for the absolute highest reliability crashes.
There are two crashes: application crashes and system crashes. Applications will crash if they are poorly written, and OS X is not a magic wand that can change that. Any computer programmer that has written a piece of software for OS X has seen a program crash, and if the programmer has not tested the program, the program will doubtless continue to crash. System crashes, when the entire operating system stop functioning, also happen on Macs. This is a kernel panic on OS X:
http://www.youtube.com/watch?v=boV9QC7dWg4
I'm not saying that this is the norm for OS X, but it is not the norm for Windows or Linux, either. Windows doesn't normally blue-screen unless you are using faulty drivers, and I have yet to see a Linux kernel-panic myself, though I have no doubt that it could happen. So anyone who says that Macs don't crash is lying.
2. Macs are easy to use. That is highly subjective. I have never found Windows difficult to use. Ubuntu, which many have described as "easy to use" was one of the most difficult things I have ever learned how to use (but also the most rewarding). Saying something is easy to use does not make it so; I could probably find lots of people who can use Windows just fine but could never use a Mac.
3. Macs are optimized for the processors they run on. So, if I look at an OS X DVD, I will find kernels for every single processor that it ran on? OS X ran on some G3s, G4s, G5s, Core Duos, Core 2 Duos, Xeons, and even Pentium 4s. So the DVD should have a kernel for each and every one of those, right? I haven't looked yet, but I'll wager a guess that it contains, at most, three kernels: a PowerPC kernel; an x86 kernel, and an x64 kernel. Compiling a kernel for each and every processor would 1.) not likely show any noticeable performance gains, and 2.) take up a lot of space on the DVD that could be used for other features.
Oh, you forget Big Macs.