I can only speak from a personal perspective. I wouldn't say I was an enthusiast, because that implies that I have for some time been reading magazines regularly, or going spotting, or actively getting involved in aviation somehow.
However, I'm not a complete novice because as far back as 13 years I was interested in being a pilot. My family are surprised how much trivia I know about a/c, but that's because Joe Public's knowledge seems to stretch as far as "that's a plane. that's a helicopter."
I'm already able to spot the more obvious types (B744, A380, BAe146) and my kids are getting quite into it too. They always ask me questions so if I don't know the answer, I tend to look it up on airliners.net and then get engrossed in various other types.