No complaints or issues with Mailfence whatsoever, I have been switching between different google alternatives for the past year now, and so far I have stayed with Mailfence the longest. Hands down the best support system I have seen so far. Quick responses and really friendly.
As for features and design, they are still improving and adding things. One of the best things is that you dont need to download anything to take advantage of the end-to-end-encryption. At the moment I am really satisfied with how everything looks and feels. It's hard to say what the product will look like in say 2 years, but it's really nice seeing a product evolve like that and being part of the journey.