I find tabbing to be inconsistent when using TAB (or Shift+TAB) on single lines vs multiple lines. If a single line is selected, using TAB will delete the line instead of tabbing it. Selecting more than one line and using TAB will behave as expected and tab. When using Ctrl + (or Ctrl +]) tabbing behaves as expected, regardless of whether multiple lines are selected or not.

I believe Tab inserts a tab unless a newline is selected. Personally I find this behaviour preferable because then I can select some text and replace it with a tab.