Has anyone tried to fill one of these? I'm just wondering how it will hold up, I want to fill it with cream cheese filling, but I have never done it before.

I use that pan for teapots - just don't use a whole lot of filling - I just use regular buttercream and it does just fine.

I wouldn't. You are risking the integrity of the cake. i only ever just put it together with buttercream.

I always dowel that cake anyhow.