Roam Research is a popular note-taking app. It's hard to say whether it's the most popular in a competitive, but it's got plenty of loyal supporters as shown by the number of people that suscribed to the 5-year-plan for 500 USD.
Recently, their lead engineer left for a YC competitor: Athens Research [1].
Is this as indicting as it looks? Or is it common? This engineer was in Roam for less than a year, so I don't think his shares were vested, so this is at least a signal that he thinks the shares in Roam are going to be worth less than shares in Athens (assuming equal participation.)
I think this is an important question for prospective users, as they're making long term investments not only money-wise but also because of data lock-in.
[1] https://twitter.com/AthensResearch/status/1414254253124866052