Can't recall seeing this promo before, but you can play Witcher 2 for free until 1pm PST this Sunday, and it's on sale for 80% off otherwise (so $3.99 for #2, and $1.99 for #1) I guess that a whole different approach then playing a limited content demo :)
Oh, they also added Etherlords 1 and 2 for a $6.99 bundle, which is cheaper than GoG. If you never played them, they are turn based MTG style deck building and tactical combat games i enjoyed back in the day. Hard to believe they're like 10 years old now.
Already own the Witchers, but man I don't think I have played Etherlords since high school. I was actually thinking about that game the other day while playing Magic 2014. I might have to pick that up.