I have been a daily logseq user for at least a couple years now, and I have not had a problem with my data being lost. I have heard of people having this issue with Synching - which I am also using - but I haven't had issues.

I like how the data storage is markdown files. I love the block centered outlier approach and use block references extensively.

I've developed some extensions too. The documentation is severely lacking here, but there are enough extensions on the (currently free and oss) marketplace that can be useful examples.

The query language is really freaking weird to me. It's clojure, datascript/datom. Not intuitive at all, but I've got several custom queries working as part of my workflow.

Overall Logseq is good software and I'd recommend it. Certainly take backups - I have from the start because of experiences like the above - but I haven't needed them yet.