When I see FR I think "full ring" so was about to pop in here with a "wtf kind of question is that?" Oops.
I concur that freerolls are good for beginners in-training. And private freerolls like CCs or bonus freerolls like the Ironman ones at FT might be worthwhile and fun. But wide open public freerolls are a grind that just are not worth the time for anybody with a modicum of skill. Unless you're just playing for grins and nothing else, once you understand the basics of the game, how to calc and use
odds, etc., then you really need to move out into real money if you want to make money, even if that means a deposit. Just do it.
Staying in public freerolls to better your game won't work beyond the very basic skill level -- you can't outplay people in public freerolls. You'll continue to see bad beat after bad beat, in frustrating frequencies, and you'll find that your sophisticated moves just don't work as they would in a higher real money game. You have no edge, it's just an extremely high-variance luckfest. It can easily lead to frustration with the overall poker experience, because whether for money or not, most people are playing to win. And when you can't consistently win, or show something for it when you do win, then the interest (and improvement) will fade out and die. And note that the penny/micro stakes are about the same as freerolls. You'll have to get up around 25NL at least before you can accumulate a consistent profit, and if you aren't willing to deposit then it's going to take quite a long and frustrating grind to build the proper BR to move to those stakes. I couldn't do it, I was much happier depositing here and there until I could accumulate both the skill and BR to play where I play now. My BR is now pretty much self-sufficient without any need for deposits, but if by some major bad swing I drop below my minimum threshold, I won't think twice about depositing again (assuming I wish to keep playing).
Just my $0.02...