Excellent one. Clue : be patient, try with the high numbers and see when it becomes impossible. Then you can add some 'X' and then it will become ... less difficult.
Beautiful puzzle! Challenging and mostly logical. If you are unsure where to start then begin with the middle vertical line b/c it's mostly symmetrical. Once you get those first few lines down, the rest falls into the puzzle pretty easily. Thanks! Had a great time completing this one! :)
Took a bit of time and temporaries at the start, but afterwards it was really quick and easy to solve. Determining the x's in the bottom corners worked really well for me.