I do the EWR-TPA about 8 times a year and find it to be difficult upgrade especially in season. I find Thursday, Friday and Monday to be the toughest. If you don't mind a connection, Northwest through either Detroit or Memphis is a pretty good bet as I even got upgraded the day before Thanksgiving which is typically one of the toughest days of the year. Was in an exit row on a jungle jet last Saturday and its got tons of leg room (more than most FC seats on bigger metal). Fare does break the tie but is it worth it for a 2:30 hour flt?