Having been getting upgraded, mostly once I board the plane. A few times being in the exit row with unlimited legroom, I've passed. Other times, I've been grateful.
CPU's are really nothing special on the equipment that UA uses domestically. Yes you get food. Yes you get free direct tv, but that's about it. Nonetheless, I was always taught to never look a gift horse in the mouth. Thank you United. I"M grateful for my status and when the CPU's come, I"m happy.