In the grand scheme of Microsoft licensing, IIS w/External Connector licensing, while not "cheap", is surprisingly reasonable (IIRC, less than $200/month per ph

In the grand scheme of Microsoft licensing, IIS w/External Connector licensing, while not "cheap", is surprisingly reasonable (IIRC, less than $200/month per physical server, including software assurance, licensing for two VMs per production server, and no charge for VMs on hot standby servers; I believe cloud pricing is similar, if not identical, and possibly cheaper on Azure), assuming trained personnel and any other required Microsoft infrastructure bits (e.g., AD, SQL Server) are already available. And for internal applications where users already have per-user Windows CALs, Windows Server is already licensed and deployed, IIS is effectively free. With that said, it's not obviously better or worse than open source alternatives in general, just different — though, at least from an admin perspective, not necessarily any more different than, say, Apache and Nginx. My own personal bias tends towards deploying on a given application's "native" platform where possible, so I'd generally only consider IIS as an application server for a Windows-native application or application developed using a primarily Microsoft stack. And, for reasons of license cost alone, I'd certainly look elsewhere for any non-revenue-generating personal applications. But in these cases at least, modern IIS releases are, in my experience, stable, reliable, extensible, securable, and as easy to deploy and configure as anything else I've used (mostly Apache and Nginx). I can't comment on scalability because I've never personally had to scale it beyond a few tens of thousands of (total, not concurrent) users. Plenty of dumpster-fire applications are implemented on top of IIS, of course, but that's true of any popular Web application server.