A Lean Enterprise survey in 2007 reflected that about 36% of lean implementations face middle management resistance as an obstacle. Approximately 28% face employee resistance. Lack of implementation know-how came second at 31%.
This is, of course, a survey conducted amongst organizations engaged in lean production. Humans being humans, I would guess that these numbers won't be very different in Software and Services industry. Basically, any change program involving humans will face challenges that are similar in nature and magnitude.
So, what skills do you think a change agent would need? Seems to me that technical knowledge is only a third of the solution.