started out with sco unix maybe in 93 gradually moved on to AIX 3yrs later my first real unix admin job. Then opportunity of becoming a real field engineer came along later and I grepped it - moved into Sun, here I played with all kinds of solaris flavors, sunos, solaris 2.3-2.4-2.5-2.5.1-2.6-7-8-9 handled all kinds of machines, from squaretop IPC box to pizzabox sparc1-20 sparc1000, ultras-to-enterprises even the clones all except E10ks, I've played with all kinds of cluster softwares, firewall softwares, backup software, all kinds of weird storage systems available to run with a sun server.
I got tired of burnt weekends working in freezing data-centers so I left and joined another company my first end user job in many years. Three years later I got bored, left and join re-joined the industry been working last few years on hpux/mcsg slowly moving into linux.
My crystal ball tells me the next big thing believe it or not is trending towards AIX. If it really comes true maybe I go into it again and start over from scratch.