I started using this after swapping from Vivaldi and looking for an alternative to their tab-grouping for firefox browsers. It's solidly alright, I like a lot of the functionality, especially banking and private groups. However, sometimes when restarting tabs will disappear. Not all of them, just a few. For example, I had several zillow listings open in a real-estate group, as well as some other sites, and after restart all zillow tabs were gone. Not a huge issue, but very inconvenient. I haven't found a throughline reason for which ones disappear and why, but this does happen on basically every restart.