Flashbacks--Alive and well?

I'm going to attempt a chapter flashback to get things moving in the opening scenes. My agent suggested it and I kind of went along with it. Flashbacks were really profuse 30 or so years ago. We were told to use them if absolutely needed and there's no way out of the jam but to use one as a last resort. I've had luck twice before using them. In fact the publisher of my sci-fi book asked for one and I guess I pulled it off.. I've always thought of them as adrenaline shots. Trouble is, that they are so damn obvious.

My 1rst chapter flashbacks are rather short and I only use them to get the steam up.  I'll go to an intriguing action scene somewhere in the book that shows some kind of obvious conflict, cut and past that over my old first chapter. I have to lead in and lead out, making sure my reader doesn't get confused. I like the "How in the hell did I ever get into this mess? opener because it belays a future scene. I then have to sew up or patch the gap I left which had the action. This wouldn't have been necessary if I hadn't had such a sluggish first act. Too much lead-up frustrates the reader--you know? Where nothing significant is really happening? I have to use a flashback because I've got three to four lethargic chapters that are clever, but contain too much dialog. If you have a slow first or even second chapter you can usually go in there and speed things up with a rewrite. You can also cut from the front, but how much are you taking away from the storyline?

Poul Anderson used an effective flashback in Virgin Planet that went straight to the problem, and then left it with a tease. It was a pretty nifty hook.

Have you ever tried a flashback, and how did it work or turn out for you?

I still believe there's some stigma or taboo attached to the flashback. I also know that a slow start out of the gate can be handled with a montage, but that requires really tight writing that covers a LOT of ground fast. Prologues also raise a lot of stink with editors and agents unless they are done very well. Two to three decades ago, prologues had their rightful place--not to sure about that today. 

This is one jam that always makes me nervous and ill at ease.

Chris