Have you ever played a free rpg?
Yes
What game was it?
Icar was the first RPG I ever ran as GM, I've played JAGS a lot too.
Who wrote it?
Icar, Rob Lang
JAGS, Marco Chacon
Where did you find it?
I found both a few years ago on google.
How did it go?
Icar had some economic balance issues (My fault), but it went well.
I just finished a well loved JAGS c13 game (Or it might not be finished, we'll see).
How did you convince your players to play?
Icar: "Lets play one of these RPG things and not get shot at paintball again."
Jags: "How'd you like to be some kind of elf thing?"
What problems were there?
Getting people to show up on time

Icar was a little tricky for a first RPG attempt, I'm not a fantasy person so Jags was tough at times (especially as my players didn't want to play have-nots).
Were there any good things about it being Free?
I didn't need to spend $90 before I could decide if I wanted to play that game or not. You also get the impression people put a lot of effort and love into the game that I don't feel looking at AD&D.
Did you print it?
No, I use a laptop.
If not, how did you get at the rules?
I game with a laptop at the table
Did it make the players want to play more Free stuff?
If the other games and scenario's are good yes. Some of my players now talk about buying material for games! I like the free rulebook/paid addon idea that i've seen with some games on Drivethrurpg.com