I get this question a lot, from both people inside and outside of the .Net community, and it came up again the other day on Quora. Below is my answer. Please keep in mind that this is my opinion, and I can’t promise that I’m right, but I can promise that this is what I really think and if you walked up on the street and asked me “should I use .Net for my startup?” this is what I would tell you.
In spite of the fact that I’m a pretty high end .Net guy, I would caution new startups that are considering using .Net. I think .Net is awesome, and I use it for my own startup HireFlo. However there's one big landmine that could handicap your startup before it even gets going, webforms.
You see, ASP.Net development is divided into 2 camps, and there are major architectural differences, and cultural differences between them.
ASP.Net MVC is awesome for startups
ASP.Net MVC is the awesome new framework that is heavily influenced by Rails and is the platform of choice for startups like StackExchange. It’s a breath of fresh air for skilled .Net developers who want a framework that embraces the way the web works instead of struggling against it. This camp is full of people who care about the craftsmanship of writing code and who like to actually ship software. A programmer in this camp is likely to be familiar with lots of open source projects, and is most likely a great fit for your startup.
WebForms is death for startups
So the answer is…Heck yes you should (as long as it’s .Net MVC)
So .Net is awesome, C# is amazing, MVC3 is hugely productive, if you find a .Net developer who works with those, I'd recommend using them. But you've got to be careful. A WebForms developer with a corporate dev background is most likely going to be death for your startup.
There are three other points I want to add that I think are relevant.
Don’t use Azure for an early stage startup
Microsoft is really pushing Azure as a platform for startups. I strongly recommend that early stage startups do not use Azure. Azure development is significantly slower than straight up .Net development that runs on a windows server or VS. Deployment takes longer, debugging takes longer, the Azure environment is difficult to replicate on your local dev computer, backups are a pain, and you're locked into a single hosting provider. It all ads up to a lot of inflexibility and friction at a time when your startup needs flexibility and speed over all other things. Azure can have a place later, when scale is your problem, but at the beginning of your startup that isn't the issue.
The ASP.Net MVC/C#/SqlServer stack scales like a madman
Listen to the middle days of the first StackOverflow podcast and you'll hear that for a long time they ran StackOverflow on a single server. They were serving a million uniques with the web app and database running on a single box! It wasn’t even a very big box. This is consistent with my experience with .Net. It scales well. So, if your startup does make it, you'll probably have a much easier time scaling the .Net stack than you would with say Ruby or PHP.
Bizspark is proof that Microsoft loves programmers and startups
If you want to build a startup on the Microsoft stack, they will give you free licenses to basically every product they make, including SQL Server, and a free MSDN gold subscription, for 3 years. They figure 3 years is long enough for you to get going so after that they want you to pay for new licenses, but here's the great part, they let you keep the licenses you're already using. So you don't wind up in a situation where you're just scraping by, then 3 years is up and you have a big Microsoft bill to pay. They don't do that, they just let you keep using the software. So Microsoft has basically taken the cost factor completely out of the equation for new startups.