Hi, I was one of your user. Only used it for several days until we removed it from our Slack group (maybe there are some other teams in the company still using it).
The reason was that it's becoming a noise in the conversations, since my team is already accustomed to use a single TZ (based on our HQ location) despite being physically in 4 separate time zones. I tried it hoping to solve the problems I thought we had, but apparently it's not.
Don't get me wrong, the idea is great and I really appreciate it. Maybe you'll need to improve it by providing a way to make it less obtrusive.
Having to do the mental conversion is always annoying (and a source of many misunderstandings if you forget to do it!). Great job with solving it , good luck with the Product Hunt launch :)