Well, few day ago I registered in SS and received it's 50 n/d The bonus is "sticky" with WR = 15xbonus on allowed games 

So, I played it and when I completed the WR (played on Desert Treasure and have fun lucky streak!) it was pretty 170.04$ in my account.

I deposited 20$ from my Visa to be able to withdraw my winnings. I deposited and received bonus on my first deposit - 20$ (account balance - 210.04$).
Then I contacted the Customer Service asking to delete the bonus from my account. I was told by Customer Service (Sean) that bonus was removed from my account (account balance - 190.04$) and I can play in any game I want and withdraw with any problem!
Then I decided to withdraw my money on my Visa (I wanted to play again - but it's for personal needs), but cannot find "Credit Card" option to withdraw. So I decided to deposit via Moneybookers to be able to withdraw by this method. I deposited 20$ from my Moneybookers acc (account balance becomes 210.04$). Then I decided to play a bit and increased my money to 220.04$! Then I decided to withdraw via Moneybookers. I asked to withdraw 215$ (wanted to play with another 5.04$). But I forgot that bonus is sticky and was able to withdraw only 170.04$ (including my 2 deposits x 20$). So, 130$ profit from n/d - not bad! Thank you, Sierra Star!
 Highly recommended!