I recently had an experience like this. Normally, I wouldn't be caught dead bringing my DS anywhere outside the home, but I noticed a lady playing Pokemon Black before class one day, so I approached her afterwards and she asked me for a battle the next time class met.
So the time rolls around; she didn't say anything before class, and I was obviously too embarrassed to ask. Suddenly, during break, when almost everyone was still sitting in the room and chatting/eating, she turned around and yelled back at me, "So, are you ready for that pokemon battle?"
At first I sat there dumbstruck and pretended she was talking to someone else, but that couldn't last long and I had to have a conversation across the room that I was, indeed, ready for that pokemon battle. I felt utterly embarrassed as I walked up to sit next to her; we did a 3vs3, since that's the only way the game will autolevel your pokemon (which is terrible, but that's a different story), and I beat her fairly easily since I don't believe she knew or likely cared about EV-training and the like.
The professor walked back in the room near the end of break as I was taking down her last pokemon, and I only hoped to god he didn't see what we were playing, since I think the guy actually had some respect for me. Nobody actually said anything, and the person that sits next to me just smiled and asked if I won or not, recounting his memories of playing as a kid.
All-in-all, I don't think anyone really cares if you play as more than a passing curiosity once you pass a certain age group. My wife and friends don't think anything of it, and people that don't know me and happened to see, well, who cares? Once you get into your twenties, I think the stigma shrinks into a curiosity. I didn't play at all in Jr. High and High School, missing everything after Red/Blue, since anyone playing would be actively stigmatized, but in my college and working years, I'm getting more comfortable with it.