I went on Crystal a few years back, I was 20-something and sharing a cabin with my parents. Overall I found the people friendly, the atmosphere was more formal - probably facilitated by efficient and formal service of the cruise itself, but not necessarily snooty.
For example, on a cruise at dinner one of the first questions asked is how many cruises have you been on, how many with company XYZ etc. At our dinner table was a very friendly and sociable couple that spends half their life on Crystal ships. To hear that, let's say, chitchatting on line at a supermarket might sound snooty, but given the context of where we were is different. The same goes true for talking about where one has travelled or what souvenir someone bought in port that day. While our financial situation may have allowed for a Crystal Cruise, it didn't allow for us to have a suite or separate cabins, or to do every World Cruise with Crystal like our tablemates. We didn't feel uncomfortable knowing that and were not made to feel uncomfortable. I think it all depends on where everyone is "coming from" and your individual comfort level with that. I've never sailed on Carnival, but judging from what I have heard from friends and family that have, I am sure Crystal will be a different, wonderful experience, and there will be much more to enjoy than to be nervous about. Bon voyage. Please post back and let us know how it was!