SQL Server really is a great database but is it worth the Microsoft tax? I've come to realize that its just not. For my own projects, I am starting to go with Postgres. I still have doubts on the performance side but based on my understanding these have largely been addressed in the latest releases.
I think using Postgres on a linux box and ASP.NET MVC as the web platform is a good compromise. Are you doing this, or have you entirely moved to Ruby on Rails (or something else)? I would love to get your thoughts on this.
I think your statement around Microsoft's reporting and BI offerings is harsh but isn't entirely off the mark. The tools are good for the simple cases but for real BI, Microsoft can't stand up to Oracle's (and others) offerings. I am sure there are companies that base their entire BI on the Microsoft stack but based on my experience, its just not common. A lot of the systems that hook into the BI stack tend to be legacy or non-Windows data sources, so in a lot of companies, purely using Microsoft isn't viable.
It's also a dangerous thing to do as Microsoft tends to use SharePoint as a glue and I would be extremely hesitant to bring SharePoint in an environment (unless its for its out-of-the-box functionality).