Not sure if this issue has been reported already, but I have lost the option to "Reply All" on the mail.bt.com web browser interface since the stupid upgrade!
Why can't BT just leave things that are working alone, don't fix it if it ain't broke.
If they must upgrade, do a pilot phase first. Also, don't outsource the upgrade to some remote IT team in south east Asia, it feels like it.
I hope no-one responds with it is down to your browser version or cookies nonesense!