We I think we ran around 10 games of Traveller over the entire weekend, with most of them during the official demo, but a few other games with interested people I happened to know or encounter.
None of the people who played identified themselves as backers, so while I can't say for sure, I don't think any of them were. I do know several of the demo attendees said they were Traveller RPG fans, and hadn't even known about the card game.
Overall the games went well. The players picked up the system easily enough, and the comments were largely positive, along with some suggestions for possible changes or alternatives. Which is always encouraging because it shows not just that they've assimilated the mechanics, but they're thinking about them.
We were using old demo decks, but we were able to show them a few images from our InDesign files. They seemed to like the icon-driven approach, though one of the players who was an old time CCGer said he tends more towards plain text.
To summarize, it seemed like a fairly common convention demo event. This was the first I'd ever held, but I'd played in my fair share. Most players reported a positive experience, a few seemed genuinely enthusiastic, and anyone who severely hated it withheld expression of the sentiment.