The interface of this tool has been very intuitive, so I did not find any problems with it at all! It's pretty fast too (even though you can't do much in less than 2 seconds). Sometimes there are some minor bugs but they're fixed quickly by their support team as well. Nothing really specific here - everything works fine :) As said above we needed an online platform for our students who were working remotely from different countries across Europe or even further away like India etc., which was quite difficult without such tools available out-of-the box. We've managed solve those issues using timelineR!