I just checked. Unless I'm missing something there is no simple volume control like on the physical keyboard? I already have the volume button on my touchbar home screen however tapping it opens a slider. I don't want or need a slider and have to do a tap and then slide to get the volume down whilst before it was one press of a button. This usually requires me to look away form what I'm doing. It's definitely a step back in terms of UX. It was perfect before the touchbar.

Thanks for pointing that feature out though. Have replaced Siri with the play button :)

Edit: Just playing around with this a bit more I noticed the expanded view now has all the normal icons. Either I missed it before or I changed something. Is there a way to make the expanded view the default?