Firefox: unfortunately, it's a bit worse than before. Instead of using the 1000 repeated lines, we tested with a 20 page cleaned Word doc that has several tables and image placeholders and formatting requirements:

 

We experienced many problems:

 

1. Scrolling delayed when using the mouse and scroll bar.

2. Focus not appearing for several seconds after clicking into the body.

3. Typing delays of 5 or more seconds quite frequently.

4. On some occassions, inability to click into the body after scrolling to the top or bottom - delays of more than 20 seconds before we could click into the content.

5. Click and type in the middle of the content produces:

 

   a. Delay before the cursor appears.

   b. Continual typing delays for several words, then no delays for a couple of sentences, then long delays again.