http://store.steampowered.com/steam_refunds/
Anyone had to do this before?

thats pretty cool !!
Quote "We do not consider it abuse to request a refund on a title that was purchased just before a sale and then immediately rebuying that title for the sale price."

Thats nice of them , seems really fair

I didnt knew this option existed?

It's only just started Hans, they should conform to the local selling laws in each country they operate in so probably set this up so they don't get sued.