I have been reading up on this lately, and the answer is definitely YES! Especially if you have a series.
I have been planning to do some sort of price promotion soon for one of my Deception series (and I will let you know how that goes), but in the meantime, check out this great infographic. The stats are really interesting.
The only thing to watch out for is whether you might have to pay money to give away your books for free. I have used a distributor for my first series of eBooks, and it seems that some stores might charge to do free giveaways. I am going to look into this further and let you know what I discover.