Just finished my flight on EVA Air. My wife and I spent the holidays with her family in the Philippines, we flew ORD-TPE-MNL-TPE-ORD. She was in prem economy, and then did a Star Alliance upgrade from TPE to MNL. I called and upgraded my fare class in economy to try and upgrade to no avail. Expert flyer showed now (I class?) and nothing opened up. I lucked out there because I was in 72H 2nd from last row on the plane with no seat behind me in row 73. Had entire row to myself. For being long haul economy, not a bad seat. I was able to upgrade immediatley after booking TPE to MNL to biz. This helped as we both were able to get lounge access in TPE and used the showers to freshen up after the long flight.
Coming back 3 days before we left, I saw about 20 open biz class seats from TPE to ORD. Checked expert flyer and I class had availablility. Called and paid the extra fare to change the fare class. This time my wife's ticket was economy but I booked prem economy coming back. The difference to change that was over 1000 dollars so I just stayed in prem economy. It was only 250-300 to change my wife's fare class and as soon as they put it thru, Star Alliance upgrade cleared immediatley. Not only was biz maybe 1/3 full, prem economy was maybe 1/4 full. There was no one else in the entire row I was in.
While I only tasted biz class on EVA from TPE to MNL, I must say it's not a bad product. Also, their premium economy isn't a bad product at all. We will def fly with them again. Morale of the story seems to be exactly what everyone else is saying though, if EF shows I availability, seems you have a good shot at applying a SAUA