What is you opinion of granting the President line item veto power?

It seems to me it would save a lot of time, energy, and money, and I wonder what the reasons were for deeming it unconstitutional. Now, if the president, or president's party dislike just one or two items in a bill, the entire thing is vetoed and has to be re-written from scratch, and p through the senate and house all over again. I really don't see how it expands executive power, as the president already has to power to just veto the whole dang thing... but I must admit I am no government expert.