So far so smooth! Everything about it has been righteous so far. And when it comes to my stack, when things come together smoothly, it makes developing a way better experience!
Recently went paid with a limit of 25 requests per collection on the free tier.
** BEWARE **
Several reviews have also pointed out it is deleting your collections and environments if you roll back to the previously free version. Happened to me as well.
What I find uniquely useful about Thunder Client is the ability to execute API calls from remote machines. This lets you make request when the API server is only accessible from within a VPN.