The Overwatch client has seen massive improvements over at Blizzcon 2017. With the community bombarding the developers with requests to make Overwatch watchable again, the developers have definitely delivered. There are still a few minor tweaks to be made regarding the client, but the difference has been mostly positive so far.
The spectator client is different for the viewers and for the observers. What we see at Blizzcon 2017 is meant for viewers, but it seems someone got a peek at the spectator client at Blizzcon 2017. In case you are interested in the same you can view the spectator client here :