In DNN 7 the strip that shows the list of modules takes a long time to load and the strip's horizonal bar which shows the rest of the modules is stuck. It seems it actually takes a I very long to scroll.
 In Chrome they work fine. I have to use Chrome to make DNN7 usable for me.

Also the color of the scroll bar is the same color as the strip's background color and there's not enough contrast to make it stand out.. For first time users, they might miss it completely. The width of the bar is also unusually narrow. I believe the scroll bar needs more work to make it more visible and easier to use.