I have been using 4.x for quite some time, and I really like it. I have looked at the 5.x beta, and I've found a few things I don't like.
In the Compose Sequences window, the <> brackets around each character make it hard to read the correct keystrokes.
In that same window, having to scroll to see all of the sequences is inconvenient. I would rather see them in a grid, without the descriptions.
Even though the window is resizeable, the characters are not. It would be nice if the characters could be made larger.
I don't see any way to select scripts within the font.
The window and sequences should be printable.