Flashbacks

One of my beta readers recently suggested that I tell part of the story of Seasons' Beginnings in flashback. Right now, Part I of the story is an expanded version of a short story I had on my old website; Part II occurs a year later and deals with the aftermath of Part I, easing the way to the next book in this series. Originally, I did not put a sharp break between these sections, and I think it's confusing some readers, hence the suggestion.

I've been mulling over the flashback idea, debating if I want to use it. It fits with the magic system of this story and would ease the transition between Parts I and II (though if I don't use the flashbacks, I will label the two parts to warn the readers what to expect). However, it is a bit late to make such a major change to the story, and I fear the flashbacks, while helping some readers, may confuse others. I really haven't come up with a good place or places to put the flashback. Probably what I need to do instead is be clearer about the time break and explain how the world has changed between the two parts. I may use a flashback in later books of the series, though.

 As a reader, how do you feel about flashback in stories? Do you like them, hate them, judge them on an individual basis? What books do you think are good or bad examples of flashbacks?