Many professional type designers as well as big names in the font industry use Glyphs. It has all features that professional font designers need, such as smart components, interpolation, kerning, hinting, even beta support for variable fonts.
There is a support forum on the website and the developers are very responsive. Cutting edge updates are released frequently. Support questions are often answered within hours and if relevant, often followed up with an updated version of the app.
An extensive PDF manual can be downloaded from the website. In addition there are in-depth articles on the website covering a large number of subjects.
If you are a student, teacher or school you can get discounted licenses. If you don't need all features of the full Glyphs version, there is also a cheaper ‘Glyphs Mini’ available.
A lot of things Glyphs does automatically for you if you stick to its rules, like OpenType feature code, building accented letters based on position anchors, ...
Glyphs contains character sets for nearly all languages. If you're not sure what characters are required e.g. for Arabic, Glyphs can tell you the requirements.
There are a large number of useful and free plugins from third party developers available through the built-in plugin manager. There are also some commercial plugins.
You should stick to the principles that Glyphs sets for you. For example, if you try to use your own glyph names, all the automatic features won't work correctly.
You can opt in to receive cutting edge updates, which are released every couple of days. These contain new features, but often introduce new bugs or change your data without being aware of it. Better stay with the official stable releases.