Personally I think double up STTs are a great way to practice bubble play. If you're at a 10 man STT and top 5 get double their buy-in (-rake). It seems like when it's down to the final 6 or 7, the game goes stale, almost like it does in every MTTs you will play when you near the bubble.
Looking at my HEM stats, the double ups I've been playing on Bodog average about a 20 minute longer time frame than a straight 10 player SnG. So in my own personal experience (and take on it) it will benefit you and help you work on "bubble play" but due to the increased average time invested the hourly rate will go down opposed to 6-max STT, 9-max STT, 10-max STT, etc.
And granted the game is boring for the most part, especially when you lose two or three players right off the bat the game gets extremely tight and the blinds increase very slowly.
Maybe a double up turbo would make it a little more action packed, faster, and more profitable/hr, I mean after all we all love action.