The 3.0 sheet that I worked with, had hundreds of HTML/CSS/JavaScript issues. Also it lacked a lot of features I wanted (and people seem to like) and some of that made it so if you use earlier versions of the sheet with the new script, it does not work, or new versions of the sheet with the old script. Working with the Roll Templates provided the most incompatibility issues, due to the Roll Templates being spread across the script AND the sheet so they had to be updated at the same time.