There is nothing about this software that I dislike in my experience with it during almost 4 years of using it daily at work.
The UI has gotten better over time but there are still issues around some features like Teams. It's also super reliable which was great as our users depend heavily upon its capabilities! Nothing really, we do not have any issues currently but support can be had if needed. This tool allows us to provide one platform all communication needs across an entire organization by combining all channels together including voice telephony calls/meetings.