The first computer our family had was a 286 12MHz running DOS 3.3 and Windows 2.11. Then came some 486SX, which I upgraded to have a double speed CD-ROM. Here in Germany dial up and downloads were very expensive, so the CD-ROM became my means to get my first Linux distribution. It was a magazine cover CD-ROM containing a DOS-bootable archive with Linux (something around Linux 1.0ish, I forgot), running the UMSDOS file system, ca. 20 MBytes. That was 1994. I played around with it for some time, until I bought my first Slackware, then my first SuSE distribution. So far this was still a hobby. I started to get paid for this as a student in 12th grade, by administering a small ISDN dial up router/server, which also hosted a Hylafax server, a Squid proxy (serving ~10 people over 64kbit ISDN), and an Email-Server. I had not enough clue about TCP/IP at that time, and I had to learn a lot the hard way.
Then I started my studies (computer science) in 1999. By 2000 I had removed Windows from my machine completely, only installing it a bit later in VMWare, for using it once in a blue moon. I wrote all my papers under Linux, did all my programming homework on it etc etc. After I graduated, I became a grad-student and did my research and all the work at the institute also under Linux (now Debian). At home I switched to Ubuntu after a few years more with OpenSuSE. Then, I got to know OS X, and switched to that for my desktop at the lab / work, and having the Debian PC be the number cruncher. Shortly before leaving university, I bought a Mac for home as well, since keeping up my Linux box was too much work at that point. Now I work for a company that makes behavioral finance software, and again I work under Debian, feeling at ease. At home, I still use and love my Mac, using MacPorts for all the good Unixy stuff, and having an OpenWRT router for toying (sometimes) and soon, hopefully, also a Raspberry Pi.
So, this year marks my 18th anniversary using Linux, and I still like it. I know that whenever I have to do CS / coding / computer work, I will always want some kind of UNIX-like system. Be it Linux, OS X, BSD or some other OS with a bash. :)