It's legit and worth it! When they have their 80% off sales, you can get $25 for $2!
The only caveat is that the $25 ones usually require you to spend $35 to use it...but get, spend $35 and you're still getting a $35 meal for $12+tip. I've never had a restaurant turn me down when using one.
Do it!
Right now they're having a 70% sale with the code "FORK" at checkout.
Search online for their coupon/discount codes whenever you shop there...they almost always have a 70% or 80% available.