The new design isn't bad per se but I have two complaints: why can't I switch off chat or disable/hide it? (Perhaps I can but I didn't look hard enough) and secondly: performance seems to suffer badly when you are reading through long discussion threads or simply scrolling down in a group to go back e.g a couple of months. They are obviously lazy loading this into the DOM and storing it inefficiently as it's equally slow in both Chrome, Safari etc. This can easily be solved by just being able to load that content more statically with page selection e.g. click on page 30 at the bottom of the screen instead of having infinite scrolling which nobody actually needs.
I still don't even have the option to switch. Not sure why. Maybe Facebook noticed my epic unfollowing of nearly everyone and everything to clean up the feed... haha.