As others have said, drinking formula all the time or in large quantities is not good for your health as a babies nutrient needs are different than adults, especially as it concerns iron.
However, if you just want to try formula and/or drink it occasionally, you should have no trouble if you are other wise healthy.
When I drink formula, I do not get diarrhea...you may or may not.
You may want to try a formula geared more toward toddlers than newborns as that may be 'better' tasting.
Some people also mix formula with other things to make it a bit more tasteful.