When I do the really old songs, people look at me like "that guy must be really old". Of course it all depends on the audience.
There are modern bands doing great swing music, but I think the audience is mostly dance clubs and older people. If you listened to 40's music as a teenager, you are most likely getting too old to dance to it now! Not to say you don't enjoy hearing it though. I enjoy it myself and I'm just a kid.
I love Stray Cats! Even that little short guy that played at the Super Bowl, can't think of his name, does some stuff similar to swing.