speaking technology wise, of course you can use .NET to build a startup product. C# is a very mature and nice language, Visual Studio is the best IDE out there,

speaking technology wise, of course you can use .NET to build a startup product. C# is a very mature and nice language, Visual Studio is the best IDE out there, beating Eclipse, XCode and TextMate hands down. Another issue is in what fields that these languages are used, what type of developer works there, and what kind of developer you need to hire next month to scale your products. Java is for banks, very big projects with integration with lots of legacy systems. .NET is more used inside of companies, integrating with Sharepoint, MS SQL server. Ruby on Rails is for hip independent developers that teach themselves and go for productivity. PHP is for easy web development. All these fields have different kind of developers that work in it. Figure out what kind of company you are, and choose technology accordingly.