Apple is Killing Linux on the Desktop
applematters.com
applematters.com
I use Linux since ever as a development platform. It works fine. Email and websurfing is ok too (thanks mozilla). But as soon as you have to write something or create and edit an image, linux software is pure crap. Compare gimp to Photoshop, open office to M$ Office or Pages? Surely you are joking, Mr. (put your name here ;o).
Linux is a hacker os made by hackers for hackers. Sometimes my impression is, kernel hackers don't have the slightest idea, what average computer users want and need. Thats why linux is marginal and will be.
Apple is making good inroads in adoption, after a few costly moves reducing its market share, is gaining and hopefully continues to gain, traction and position itself as the consumer alternative to the nightmare of Windows. Linux is many different things, but the gain of community supported, easy to install, open source software will likely continue making inroads into the proprietary world. It remains to be seen if Linux can bridge enough proprietary apps to address the needs of Joe user.
In many of these systems, an important factor is the software ecosystem surrounding the OS itself: Windows has had this major boost and resistance to competition based on its 1-2 orders of magnitude greater availability of software than any of its competitors, but OS X is attracting a number of niche apps with major strong appeal to some user factions, and Linux is finally getting easy to use methods to access the plethora of good apps that make an OS stick.
Even for hackers, OS X has the advantage of being able to run most Linux/Unix applications in addition to all the excellent OS X apps.
If you ask any random linux admin a question, the reply will be "You use that crappy version from last week? Install the latest version, THAT is the one that does it right."
Thats true for any version at any time.
If so, that's not what made me switch. I switched to a MacBook because 1) Suspend/resume would work reliably, 2) I would be able to plug in an external monitor and have it work without having to restart X and 3) I would be able to easily attach to WiFi networks, especially those using modern encryption.
Having supported hardware is a huge plus on laptops.
So I still use Linux on my desktop and I prefer X window managers to the Finder or whatever OSX's window manager is called. I also think that Linux package management is vastly superior to the mismash of package management options available on OSX.
For more recent examples, I'd look to graphics and multimedia editing applications (e.g. Avid, Final Cut Pro, Photoshop, etc).
Most businesses I know might give a Mac to their designers, but the rest of the pack has to live with PCs.
Also, since you mention those "old" killer apps, apparently they were not killer apps enough to gain the Mac a significant marketshare a few years ago. So I question their deadliness.
As others have mentioned, the killer app for the Mac at the moment is being a unix box that "just works" and lets people get back to coding.