I have tried with some smaller test projects and I am quite impressed with how smooth it ran. Not enough experience, but the two takeaways I have so far would be:
- (for Android) Don't overwrite the _draw function for custom drawing in 2D. It went very slow (at least I think this was the reason...)
- Do not rely on "mouse entered" or "mouse exited" to track mouse position, because a mobile user will only tap and drag, not "hover". I guess this is obvious but I completely overlooked it.
On the Godot sub-reddit people are quite regularly sharing mobile games made in Godot. Would recommend you to have a look there if you're interested.