I am a season ticket holder for 129. Section 129 is one of the best places for Eagles games if you want the rowdy football atmosphere with the high fives all around. There is no better place to watch the Eagles score a touchdown. There are 34 rows total in the section but you won't want to venture any higher than row 20. If you sit too high up, you won't be able to see the plays in the back of the endzone because the endzones sit so far back; not up. You will instead have to go by the crowd's reaction. However, if you sit too low and close to the field, it will be extremely hard to judge the depth of the field when the ball is on the opposite side of the field, especially on running plays. I would say rows 8-17 are the most ideal for section 129.
You can easily get to section 129 via the Comcast entrance (Headhouse plaza side) or the North East gate.
The Headhouse plaza is the place to be if you don't have a spot to tailgate.