A widely used file system is likely to be more mature than a specialized file system used by few. This is especially true for open source products. A mature file system has fewer bugs, and it typically also has more support tools and documentation.
The open source community supports both mature and less mature (more experimental) file systems. Generally speaking, a more mature file system has an older design, lacks certain research-oriented features, but also has stability and plenty of tools to support it. On the other hand, new file systems that incorporate many high-end features for performance, security or capacity are less mature.