I think I was about 5 or 6 when I first saw it. I only remember vaguely, but I think I have the picture of "Just Dig" or some dirt style level in my head. I didn't want to play it though, I just wanted to watch someone else play.
When I had got a little older I browsed with a friend of mine though the various games, but we found Supaplex first and just played it not continuing searching.
I remember in elementary school we had an old comp. and played various games there too. I almost never played actively there though, but I remember us standing around the screen in a crowd watching; this were my only contacts to lemmings at that time.
After moving, I think in 2001, I began to play again, among other games also lemmings. I used to play a game for a few weeks or months, and after that I switched to another one. After some time, when I had played a couple of games, the cycle restarted and I continued games I played before. In 2003 I somehow found LemEdit and created a few levels, nothing special though. At the end of that year I found the Supaplex forum and stopped playing other games for over a year. In the beginning of 2005 I somehow got the feeling that I wanted to play lemmings again, and continued playing the original levels/ONML with WinLemm, later I registered here. I think the rest you may know. I still neither completed the original levels nor ONML, but at least for ONML I'm going to do it.
And yeah, I have to agree with DragonsLover, I somehow think that the older games are better. Why else should I still playing them while so many new ones exist?
Oh, and I just want to say again @JM, I didn't find those two feature, I just was the first one making a level supporting them. I got that information reading the conversation between ccexplore and Mindless in some thread, and after that I guessed that for the vgaspec file it might be the byte mentioned in rt's level format description.