1) When uChat was first rolled out the team who ran the rollout did everything they could to make it seem as though they had created uChat from scratch and that it was an internal tool, even though everyone knew it wasn't. The rollout was comically inefficient and the platform didn't scale at all to Uber's size. The uChat team then tried at an all-hands to talk about what a great job they had done building uChat which was followed by a slew of questions around all of uChat's massive failings such that the CEO started grilling them a bit. It was both embarrassing and strangely funny to watch what was either their total lack of self-awareness or their blatant misrepresentation of everything they had done.
2) When I left Uber in November of last year, uChat was still pretty dysfunctional. I use Slack today in my new role and it's a MASSIVE step up.