I normally book a JS and have stayed in a GS once on Symphony - nice upgrade, loved the perks and Coastal Kitchen.
The upcoming cruise on Adventure, I had a JS through the casino. When the Royal up email came, I thought what the heck and put in ridiculous low offers on a GS and an OS. I was shocked when I received the congratulations you have been upgraded to an OS email.
I know the benefits of the OS on Adventure are less than other ships but that's ok with me this time around.