I'm a stickler for systems that are extremely reliable. I honestly have apps that have been running for over 2 decades - albeit in virtual XP now. But who's fault is that - MS!
I've built a number of websites and other apps that required .net and all have had problems - always the fault of some .net quirk or .net upgrade. I still run both linux and MS web services. By far the most reliable, economical, and feature intensive are the linux systems. The open source community is kicking butt! Maybe that's why MS is looking at joining.
Build something using Linux, Javascript, PHP, C/C++, Perl, ..., - for the most part it works reliably with little downtime or maintenance required.
I work on mostly Windows systems, but I had an Ironport MTA appliance running a *nix derivative of some kind, and a quirk in the regex implementation of the Java version it was running drove me freaking nuts for 2 days.