That doesnt deserve a ! or a !!
Not many moves really deserve a ! unless its a far from obvious subtle move, eg usually NOT a capture, or even a sacrifice.
A major sacrifice may deserve a !.
That rook sacrifice however was somewhat obvious, so not a !.
If the advantage in the sacrifice is like positional or leads to an advantage not instantly, then a ! may be provided or something
I know im being generalised, but thats my perception :D
Ne4 is SO not ! or !! =P
is this a "!" ?
If this is also a natural continuation I think I'll lose faith in my chess (quality of move recognition) ability :P