So far what I knew are StackOverFlow.com and PlentyOfFish.com
1- The stackoverflow engine is a great example. Also you have the power of SilverLight, if you want to make your application interactive.
2- You are not really locked in, you should just pay the server licenses. Expensive, but that's the price you pay for using MS products. Read Jeff Articles about StackOverFlow, they have mentioned licensing and its matters.
3- Not So Cool? You already said, it has an awesome IDE?