I've found it on the whole very good for building small games.
Some caveats though, it seems off the bat far to difficult to get a good PBR environment, the default procedural one for example is a blue sky and makes all the models render with a blue cast. Whether this is meant to happen and would be cured by a different sky I don't know, as they don't provide any example skies to get started with(!). So I've just been using a clear colour instead of sky which seems to give you more simple shaders.
Second, up till 3.1 they only supported OpenGL ES 3.0 which meant for me no android versions as my devices were only ES 2.0. Now they support ES 2.0, but there still may be bugs in their implementation, and in addition lots of ES 2.0 devices ship with bugs so you need workarounds. I've yet to see how this pans out.
I've also had trouble importing looped animations, whether this is due to their better collada blender plugin, or the engine code itself, or that I'm not doing something correct, I don't know, because there is lack of tutorials. But there have been some improvements to the animation system in 3.1 so I need to check this out.
Lack of tutorials can be a problem in general, but this is mitigated to an extent because the whole thing is designed to be as 'self documenting' and simple as possible. It is hard to complain though, as a community effort, because I've realised that *I* should be contributing tutorials, that's the only way there will be more.
The other thing is that to my knowledge there isn't much of an asset store compared to say, Unity, so it will currently appeal less to people who like building things out of pre-made assets. On the other side of the coin the asset system in Unity it is far too easy to bloat + bork your project, so it is nice to not have that temptation. It also is very actively worked on, which is both a plus point and a negative, because it is in a constant state of flux.
That reminds me it is really easy to make backups of your projects in Godot, this is a major plus point for me. I can zip up e.g. my chess project without bigger assets like music and sound, and it comes to a whopping 36K, and project files are sensibly designed and in human readable / editable form. I found making backups in Unity to be an absolute pain, partly because it seemed impossible to avoid mixing scripts and assets.
That said there are plenty of good engines to try out there, I see Esenthel engine is now free that looks worth a look. 
