The reasons for advising people to get Apple laptops instead of a Windows laptop were straightforward. Mac OS X was miles ahead of the dreadful Windows XP (I hate XP with a passion), and Vista wasn't much of an improvement. Mac OS X was easier to work with, more stable, generally more pleasant to use.
On top of that, the iBook and PowerBook were so much better than competing Windows offerings it stopped being funny. Sure, raw performance wasn't their strongest point, but everything else was. They had better build quality, were lighter, thinner, and prettier, and, if you go back far enough, they were distinctive (when I toted an iBook around at university back in 2004-2005, I was the only one). The first Intel-based Apple laptops continued this trend.
When Windows 7 was released, one major advantage of Apple laptops - a better operating system - vanished. At least, it did for most people, including myself. For me, Windows 7 is faster, lighter, and easier to use than Mac OS X, and when it was released, I pretty much dropped Mac OS X like a stone. While this won't apply to everyone, operating system surely is no longer a truly valid reason to pry people away from Windows.
As great as Windows 7 was, Apple still had the better hardware. Especially the MacBook Air (except maybe the first generation due to its price) showed us what laptops ought to be like, but with the Air's internals being designed by Intel, it would only be a matter of time before similar notebooks would pop up for Windows.
And they did, and we know them as ultrabooks. So, when my MacBook Air was up for replacement late last year, I jumped ship to Windows laptops - for the first time since 2004. After looking at what the market had to offer, I chose Asus' ZenBook, and while it took them a few driver versions to work the kinks out of the dodgy touchpad, I couldn't be happier.
Build quality is phenomenal - solid, no flexing. I prefer the ZenBook's dark and angular design over the Air's light, rounder design; the ZenBook feels and looks more professional. The ZenBook's Bang & Olufsen speakers are so much better than Apple's flimsy speakers they alone could be a deciding factor if you watch a lot of video on your laptop (like I do). Sleep/wake is instant, and cold boot and shutdown take only a few seconds.
It's not quite up to Apple standards in all areas, though; the keyboard is slightly less pleasant to type on, and the touchpad, while quite good with the latest drivers, is simply still not up to the exquisite quality of Apple's (a Windows 7 issue, actually, since the exact same drivers on Windows 8 deliver an Apple-quality experience).
So, when my aunt, long-time Windows user, called me this weekend and asked me to buy a laptop for her, I didn't rattle off my usual list of reasons to go Apple. Instead, I told her I'd buy her a ZenBook, since it comes with the software she knows and likes (Windows), and it's almost every bit as good as an Air. Those few areas where Apple still has an edge are simply not enough to justify ripping her away from the software she likes.
As crazy as this sounds, this was actually a bit of a big deal for me. I've grown so accustomed to convincing people to buy Apple laptops that it felt like ending an era - an era that started with my favourite laptop of all time (if I still had it, I would kiss my iBook G4 goodnight every night), but which has now ended with ultrabooks. They won't do anything to stop Cupertino's stellar laptop shipments, but I personally no longer see a reason to steer people towards MacBooks (unless they specifically want to, of course).
That being said, I'll hold on to that standard list of reasons to buy Apple laptops. After all, Windows 8 is right around the corner.