Is it worth to use it? What do you usually get??

Usually a few CSC or a CS item. But I suggest you use it, not many will buy it at Shop Search price anyways.

Plus you get achievements for finding and using it.

well sometimes you get an item sometimes you get Cash shop credits. I wouldn't use it since it's worth a lot but it's your choice

well I used it, I got the achievement but the item was not worth at all, i got a Vanilla Star Struck Tank :(

I got some crappy sticker so no worries, that's part of reason they don't sell for a 10 mill each :P