I've got diffuse esophageal spasm. What consequences should I be looking for?

Chest pain/dysphagia. Chest pain and/or difficulty swallowing and/or pain while swallowing. If you have barrett's esophagus, you're at risk for esophageal cancer. If you haven't had endoscopy yet (i assume you have since you know this diagnosis), you should see a gastroenterologist if you haven't already.
Chest PAIN from DES. Des is a motility disorder of esophageal function. The muscles of the esophagus forcibly tighten, typically unpredictably, resulting in severe chest pain. Distinguish this from situational esophageal spasm, "nutcracker esophagus", and of course non-esophageal causes of chest pain. Speak with your gastroenterologist about rx options to minimize attacks, where to go/ what to take when pain develops.