I don't know about that. Before WWII Fighters (janes) was released I downloaded the demo and couldn't wait until the game was released (a long time over here in Oz!) The demo sold me the game.
At the time it was a choice between EAW and WWII Fighters. I didn't have the money to buy both and I went the Janes route. And even now I don't think I made a bad descion. (Trying to fly a multiplayer game over the internet is a bummer in Australia. The ping rates are so low people laugh at you if you ask to join in.)
I flew the EAW demo first and it was fantastic, then I got the WII Fighters demo!
I recently upgraded my PC and I've started to go through the campaigns again. Whoo Hoo its like a whole new game with 3d clouds and 30FPS.
B17 sounds like a great sim and I want to get it... but a few other sims are comming out roughly at the same time (Fighter Nations for example) Now I can't affort to buy too many games(Too many small noisy mouths to feed! The 'Trouble and Strife' is already giving me stange looks! "Nothing dear just writing a letter about flower arraging! Nothing to do with Flight Sim's...")
So I wouldn't mind trying the game before I fork out the cash. (Unlike America, we don't have shops that'll let you return a used game over here!)
Anyway the whole point of this letter is... If the game is really good then releasing a demo is a great way to cut through all the hype and show the people what their buying.
It's a great way to sell sell a game!
(you don't buy cars without test driving them. Sims should be the same!)