This paper discusses the practical challenges and lessons learned in implementing and testing three types of model predictive control (MPC) solutions (ON/OFF unit, dual-fuel, and VRF systems) in small and medium commercial buildings (SMCBs) as part of efforts to create grid-interactive efficient buildings (GEBs). It highlights the potential benefits of MPC technology, especially with recent low-cost advancements, but emphasizes the real-world difficulties in deployment. Key focus areas include site selection, eligibility, retrofit availability, modeling automation, and best practices for end-user interaction and error management to ensure successful operations.