I love the fact that you can cast to groups and chromecasts through the app, but it'd be great if it was possible to change what you're casting to instead of disabling the cast and then re-casting to the new device/group. So, whilst casting, you can still see the other groups/devices available to select.
Google themselves only just started doing this recently, so not sure if it's available for others to do, but it'd be great if you could!