Today it seems to be bringing up the login screen almost every time I come back to the window.
I'd think the advent of threading support in modern desktop, mobile, and webmail clients has eliminated the need for wholesale quoting of previous messages in a 2-person back & forth.
If you're getting rememberme issues, have you tried clearing cache and cookies related to the beta? I'm unable to reproduce at my end so there could be something going on there.