Ask HN: Choosing between Microsoft and everything else

I'm a software engineering student in his twenties. My work experience has mostly been with Windows technologies (.NET, SQL Server, Windows Server, etc.) and Java for Jenkins plugins. At home, I have a Windows PC and a Macbook, but mostly develop on the latter with frameworks like Django and Rails, in Vim.

I know a guy at work in his fifties who long ago decided to use Microsoft technologies exclusively, and I've never seen someone so happy to code, because he only has one ecosystem to work with and it works well. I've also been bit by the Microsoft bug, but I can't bring myself to use their tools outside of work. Visual Studio's a great IDE (especially as of late), and C# is a really fun language, but the license costs are enormous, MSDNAA licenses are for personal use only, and Azure generally costs a lot more than a VM on Linode or Digital Ocean. BizSpark also isn't an option unless you're seriously starting a business.

I feel like I'm at a crossroads of sorts, like my coworker once has been. I prefer my experience with Microsoft, but its costs and vendor lock-in are hard to ignore. I've tried Mono, and it's slowly getting there, but until vNext is production-ready and I can give it a serious try, I won't consider it a viable option.

I'd just like to know if anyone else has had this experience, and if so, what led them to choose one path over another. Any advice is also welcome.

EDIT: I'd just like to clarify that I'm not trying to choose one platform for the rest of my life, in every aspect of it. I don't mind learning one tool over another in a work context, but I have an interest for the startup/entrepreneurial world, and that's when choosing Microsoft isn't as easy as choosing anything else.