I think this is an intentional interaction design. When you are always working with hundreds or thousands of source files, tabs kind of lose their meaning. The fuzzy-search quick open panel and project-wide find become your main dependency for quickly jumping around your codebase (with the benefit that you don't need to touch the mouse).
Preferences → Navigation → Double Click Navigation → Uses Separate Tab
Because that's what they are.
There's a lot of attention on .NET Native. Given that LLILC went from nothing to being able to build and JIT Roslyn in 6 months...
Let's just say I have some speculation in mind.
I'm primarily a Python guy and with the 2/3 split, I've had my eye on .Net Core to migrate my business platform to. Pretty much been looking to dump Python for anything over a line count of 500 and keep it that way. I'm open to any speculation as to where it's going because I'm finding the .Net platform to be more attractive than ever. A few years ago it was looking pretty sad but MS really turned it around and I'm interested in a permanent migration. I really can't find much, that I enjoy using, that approaches Python's broad use cases than C# on .Net. With dotNet Native and Xamarin, I'm very seriously considering the plunge.
Visual Studio feels a lot more "enterprise-y" than Xcode and offers a lot more advanced features and tools on pretty much all fronts, especially in the UI (e.g.: Xcode doesn't even have file tabs, but sth. I'd describe as big "whole-UI-tabs"). But...
Xcode has llvm. This compiler and it's tools (i.e. the analyzer, debugger, etc.) just make VS' compiler look like it's from the 90s. Really.
-> Have you ever heard of llvm's "address sanitizer"? Forget the days of endless debugging! This little helper has revolutionized my debugging productivity and solved so many little subtile bugs for me...
So in the end you'll loose a lot of nice UI gimmicks and additional tools, but the compiler suite makes up for that.
And even if you don't need those llvm features, you still get a unix environment, which makes working on many fronts a lot easier. E.g. I'm primarely working on different kinds of web servers: To test everything I can just install whatever I need... brew, curl, netcat, wrk, ... And it will just work. And let's not forget all those "standard" unix tools like find, xargs, grep, etc.!