For me -i.e. as a man, hearing that about a woman -it sounds great. It can mean all kinds of things, like her being low-maintenance, not stubborn or picky about most things, and she may follow strong leadership with ease.
Of course that all sounds fantastic, since that fits with my traditional leanings, my perspective on how relationships work (a la requiring great flexibility from both partners) and my penchant in naturally embracing the mantle of leadership (it's in my blood and part of my heritage, but that's a story about my Grandfather for another time) but how the trait manifests will be different from person to person.
I have, however, noticed that sometimes when a person says they are the easygoing/flexible type, it may mean they are just indecisive, which has me wondering: What happens when the person becomes less indecisive as they grow? While they learn to make concrete choices more readily and develop personal tastes/preferences for themselves, do they become more difficult to deal with? Will they be inflexible?
Figures that I'd be concerned about the long-term for something like this. But a slice of the present doesn't always translate into the future, and while I trust character, some parts of a person develop into character over time.
I'd like to hear your opinions, and I'll be searching for some experience and wisdom on the matter. I'll keep y'all posted.