I'd wager this 'learning curve' myth was started by those who are familiar with PS and the like who tried GIMP and found it different. Not difficult. Just different. I'd also wager that those wholly familiar with GIMP would similarly label PS as 'having a steep learning curve' merely because it's different. It's not that one or the other is truly difficult to learn, it's just than once you become conditioned and comfortable with one system, it seems difficult to learn another. Just like most adults find it difficult to learn another language.