Regarding stability - I don't find Project 2010 to be any more or less stable. They key is to ensure that you have Project 2007 (or any other release) fully patched. Project 2007 is up to SP 3 and Project 2010 is at SP-1 plus several cumulative updates.

Regarding what is shown in a split (combination view) - no - it hasn't changed in Project 2010. What is visible in a lower pane is dependent upon what you have selected in the upper pane.

You could open a second window showing the Gantt chart (Window, New Window) and arrange the two windows so you can see all data.