Here are some differences that exist on the different platforms.
Windows 4C Client
For multi line text fields, the scrollbars are only visible when the
length of the field is greater than the total columns * total rows.
If you need them to be visible just make sure that the format specified
in the display field definition is at least one greater than the
#rows * #cols.
MacOS X 4C Client
For the MacOS X Client, <ctrl>+<return> cannot be used to insert a new line
into a multi line text field.
Use <option>+<return> to do so instead.
For multi line text fields, the scrollbars are always there.