Yeah, I also feel like flash forwards have a danger of being cheap, like the storytelling equivalent of telling your readers "I promise it gets better later!" in lieu of figuring out how to give your story a good hook. They can work, and it's possible to do really cool stuff with the expectations created by doing a flash-forward, but I feel like that should be their purpose -- not "I have to let readers see a sneak peek so they aren't bored by the beginning" but "if readers know this element is coming, that's going to change how they see the beginning of the story in a cool way."
For me there's also a danger of making the early part of the story feel like a chore -- I want to get to the part where that stuff is happening but first I have to wade through all this other stuff. Instead of building up from reluctant farmboy to awesome hero, I'm bored and frustrated with reluctant farmboy because I saw a glimpse of swordfighting hero want him to get to the hero part that got me interested in this story. So yeah, you've hooked me by promising rad swordfights later, but you've also cheapened my ability to invest in this character prior to the swordfighting.
So I would say, be careful with flash-forwards, and think about -- does the flash-forward have some narrative effect on the story, where the readers seeing what will become of a character makes them view the story differently, or set up information that will be important later? Or is this just reassuring readers "I know the opening is boring, but it'll get better, I promise?" because if that's the case, then.... I feel like a flash-forward would technically work, but it would be much better to either make the opening compelling, or skip it and just start your story at the point where things get interesting.
