Do 5HT4 agonists such as Metoclopramide actually lead to improvement in symptoms for patients with diabetes related gastroparesis?  

Yes, sometimes when the gastroparesis is frequent or the symptoms are tough, I do use Reglan to help. By the time they wind up in the hospital, they are really willing to have me use anything on them that might help. I explain to every patient the side effects of Reglan, including tartive dyskinesia...