Yes, multi-row text input areas (most commonly found in the forums and wiki areas) now use the normal site font by default. This was done primarily so when you're writing a forum post you can see it more like it will be shown, and it's generally nicer to look at.
But of course some people will prefer to keep a monospaced font for these areas, so an option for that has been added to the user area. Go to your user page
and click the Forum Settings link. It's at the bottom of the first section.