I actually didn't plan to switch. Years ago I touched Apple briefly because I built an Apple ][ (I got bored, don't ask), but then started with PCs using DoubleDOS, MSDOS 3.2 (I think), Worries for Workgroups and anything following, as well as just about any UNIX going (SunOS, Solaris, AIX, HP UX, SCO, *BSD and Linux) until I sort of settled on a combination of Windows XP and OpenSuSE.
However, I bought a MacbookPro as part of the research for a book I'm writing as the battery life seemed attractive and I needed to work with OSX for the book to be complete. When I started to use it properly (after accepting that Apple doesn't seem to think much about decent keyboard navigation by omitting Home/End/PgUp/PgDn and even Delete keys) I discovered OSX was probably the most productive platform I'd used in a while - no distractions, no endless interruptions for updates patches and virus scans (well, OK; until I mistakenly allowed Adobe products onto the machine), and as a laptop the Macbook beats the bejeezes out of all the other ones I'd used so far - and none of them were exactly cheap either.
In the 6 months following purchase I converted to OSX, with the last vestiges of Windows now hiding in a Parallels partition which I use every 2 weeks or so (and I have to plan for as it takes a good 10 minutes for it to catch up with patching). I sold 2 laptops and one desktop, with one left on standby as standalone Windows/Linux box which holds things I haven't got around to convert. I use OpenOffice and occasionally iWorks (although I still haven't worked out how to do my own templates as a sort of home approach to DTP), and for client compatibility I have MS Office for Mac (thankfully the version before the infamous productivity killer the "ribbon" was introduced). I use Omnigraffle for diagrams and a bunch of other things, and in the background I have compilers installed to use stuff like Wireshark and Etherape if I want to go under the hood to use its BSD origins.
The list of "better than Windows" doesn't end there, but I'm sure you have other things to read.
I have been recommending the silly thing ever since(*)
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Just one thing you will have to pry from my cold dead fingers: for precision work I still prefer my trusty Logitech Anywhere MX mouse over the trackpad or the Apple mouse (which is too flat, and I *like* buttons
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(*) As a matter of fact, especially where security demands are high I see more and more Macs appear because it's simply less work to keep the system contained. I know of a number of Swiss private banks which have switched wholesale, but I don't know how well Apple has developed enterprise management for OSX. The gap here is decent file storage..