I also started with Battle Masters, without having any clue what it was. Just a random Christmas present my brother and I would play in the early 90s. My first actual encounter with 40K was a Bolt Thrower CD my friend let me borrow; I loved the cover and he told me what it was from. Then I started noticing them at a hobby shop (my dad was into model trains). Also ads for the Space Hulk PC game.
Never heard about it again, until the trailers for Space Marine came out. I immediately thought it was the most badass thing I had ever seen, even for having barely any experience with the hobby. I was coming off a 4-5 year WoW addiction, so the interest is understandable. Played the demo and nearly shit my pants at the sheer brutality and blind gothic ignorance/awesomeness of it all. Started looking into the minis and background, dropped the money for AoBR, and the rest is history. Built my Orks to about 1250 (building everything exactly like the box with no clue of tactics). Then I stripped the Ultramarines I painted, went Black Templar, and built to almost 3k. Now they suck hard, and started back on the Orks.
I honestly said to myself where has this hobby been all my life? I used to dick off, buy fast cars, drive around all day burnin gas and getting pulled over, and playing WoW when I wasnt doing that. Now Im productive and creative, take pride in my work, meet new people and throw beerhammer games every weekend. Getting into this hobby has been a great move for me, even with the crap GW throws our way, the experience has been totally worth it.