Previously, I used Apache, but it wasn't stable enough.

I have used JBoss and open-source Tomcat. Depending on the use we will use a particular solution. For example, if we use .NET as a core, we will use IIS.

Previously, we used Apache, Orache and Webinar Technologies.

I did not previously use a different solution. This is the first tool of its kind that I have used. 

I previously used Microsoft Active Directory. I started using IIS to see how can I deploy a secure certificate from my organization. Deploying certificates often require payment for various services. However, if you have a Windows Server, you can deploy it on-premises without having to go online. However, if you opt to avoid going online, you'll need to have an alternative process in place.

Frankly, we are using other web server applications like the Apache web server. It depends on the application, and how or what web service application it was developed. If it was developed to be used with the IIS, then we use IIS for that application. If this application was developed for Apache or another web service, then we will install this webserver to run the application. Most of the time when it is a PHP web application, then we will use the Apache web server rather than the IIS. But if it's ASP.NET or another .NET technology, then we will use IIS. Or if we are using, for example, another solution from Microsoft, such as SharePoint or Microsoft Exchange mail servers, et cetera, then we will be forced to use the IIS service. Sometimes, you don't have a choice to choose. If it's a Microsoft solution you want to deploy, you will be forced to use IIS. If it's in-house developed application or you buy a product that needs a web server, then you can choose, but it depends also on the compatibility list of the application.

I have not used another solution previously.

We also use Apache Web Server side by side with IIS.

I have experience with Apache Web Server, WAMP, and XAMPP.

I have tried other tools (such as Apache), and found that IIS is more stable and easier on the memory for low resource systems.

In addition to this solution, we have worked with Apache Tomcat for Linux.

The choice of solution is dictated by the customer's requirements. If it is a Java application then we need to use Tomcat or Apache. If it's a .NET application in use then you need to use the IIS. It isn't a personal choice, or whether one is better than the other. Rather, it is about the application.

We switched because of the nature of the application and technology.

Yes, we used RSA Radius. It was very hard to maintain and outdated.

From the beginning, we have been using Microsoft products as our base solution. We have Unix and Apache and those things in addition in the places where we need them, but we are mainly running on IIS and Windows.  

We've used this platform from the beginning.