I don't use Excel enough to get excited about new formulas and functions. That said, in reading the comments on Mike's video it appears that Excel power-users are excited about the new features.
The video about new whiteboard features in Microsoft Teams is the one that I got excited about. In particular, I can see a lot utility in being able to aggregate reactions and saving pen settings for use between whiteboards. The new option to drag an image from my desktop to a whiteboard is also very convenient (I love anything that removes having to use file explorer to upload).