I was in 29K on a 50J 747 recently. There were only two seats in the exit row in front of me (as was clear from the seat map) and it was one of the best long haul flights I've had in Y. Plenty of room to stretch the legs, but no problem with people congregating in front of me (as is the case with row 28), and room to squeeze out forwards.

The caveat is that if the person sat in 28K (whatever they label it) had been larger than she was, had splayed her legs more (now now children, behave yourselves), or had put bags on the floor to her right I may not have been able to get out nearly so easily.

All in all though, I would certainly recommend these seats.