I don't think the average/mean level has changed much, but I do think that the overall [i]range[/i] of quality encapsulated in "Casual" has increased a little bit. It's the area most people naturally gravitate towards, as has already been noted. And with a new site, and a lot of new members, there's been a huge influx into Casual - where everyone starts testing the waters - while the activity of Free and Advanced suffers. Over time, I think stronger Free/Advanced communities will establish themselves as people figure their level relative to others out and gravitate towards others of similar dedication/ability/whatever, and the boundaries will become clearer again as (comparative) activity picks up in Free/Advanced (not that they were ever that defined and clear in the first place.)

Of course, I'm not the best person to gauge the situation, as I've almost exclusively RP'd in "High-Casual" RPs at the top end of Casual (read: too scared/not enough time to go into Advanced). So I don't have the broadest view of such things.

EDIT: Sorry, didn't realise this was 3 weeks old.