The easy to use interface, it's fast performance even in low end computers (I have one laptop with 4gb of ram), I've been using this engine since it was first released because they supported all my needs so far; now that there are more features available than before, my only problem here would be its price which can't go up too much without losing their popularity among developers who do not consider money as something important when developing software like vnd3d does.
It has helped me develop several small projects very quickly while keeping them free or almost completely free compared to other engines such as Unity etc., also being able to monetize your applications easily by simply adding ads makes things easier for you if you don't want to rely solely on donations from users but still need some extra income to keep going.