Hello,
As I was the beta-tester of the lablqml, I can share some of my experience :)
I've written an example[1] that creates a couple of views on top of
OCaml-created data models, emits signals from OCaml, calls OCaml
callbacks from QML and so on. It can be taken into account as some proof
of concept.
At first, as Dmitry said there's some simple hardcoded startup, but it was added on behalf of my request (I wanted one to be able to use GUI without writing any line of C++ code). However one can still put their own startup in C++.
Second, the developer still must deal with C++ compilation and linking OCaml object files with C++ ones. AFAIK, Dmitry intends to improve the process in some future, but currently it a bit tricky. I haven't tried native OCaml build systems (such as ocamlbuild or omake) with it yet, but using the Makefile one can see, that they have to manually resolve all the Qt libraries to link with.
Third, there're still some issues. E.g. creating the data item object used in view, I was unable to create a mutable property that can be used on top level of delegate[2] so I had to expose[3] the object itself and access its property, otherwise property changes weren't revealed to QML.
But anyway while lablqt is still to be considered as some beta release, I claim that it is already more usable than e.g. lablgtk.
[1]