As someone who is relatively new to BGA, there are some things I like about the change and some I don't. It probably bothers me less because I have had less time to develop muscle memory and familiarity with the old format.
What I most like: symbols/color coding in the side menu for casual vs. arena games. The subtle progress bar that visually shows the % complete the game is. However, as someone with several colorblind family members/coworkers, I know that this would be completely unhelpful for them. Even for those that aren't, we have to squint a little to see the progress, due to the color difference being *so* subtle--especially when there's text over it.
What I most dislike: the removal of spinning hourglass that replaced the avatar of the player whose turn it was (as buggy/laggy as that could be sometimes). It was very easy to glance and see if it was almost my turn (or if the game was at a stage when everyone had to make a selection, like in Heat). I can't remember the turn order of every game in progress, so seeing the name of whose turn it is tells me almost nothing.
One other thing that has been confusing: when in the forums, you can't close the side panel (the one that opens when you click your avatar) by clicking anywhere outside the panel--like you can on other pages. To close it on a forum page, you have to click somewhere in the page header (top white bar), or on your avatar. I could be wrong but I think this changed with the other updates, and it has made the UX on the forums worse.
One final thought: change is always hard for all of us...but I always remind myself that only living things experience meaningful change.