As the title blatantly states, what feature are you grateful for that Cardsmith has now, which it didn't have when you joined?
As someone who's been here since the beginning of the site, I'd say I'm split between integrating Disqus or integrating a user login. Yes, there was a point in time where MTGCS did not have either feature.
Edit : To expand, originally, below the artist input line, there was a separate line to enter your identity. If you left it blank, it'd label the creator Anonymous, of course, but the issue was that any one could just type in whatever your identity was, and claim it was you. I don't think anyone from those days actually did it, since it wasn't long before the site added actual user functionality. And no one would know anyway, because back then the site didn't use Disqus.