SharpDevelop is actually pretty awesome. It's totally open source. The actual compilers are free and come with .NET when you download/install it. Microsoft likes to hide that. Visual Studio just an IDE, not a compiler.
http://www.icsharpcode.net/opensource/sd/
I've used it for C# console programming for a few months. I've never used the forms like in the screenshot.
But yeah, I like how I was able to quickly pick up both the PHP & C# languages. I'd stick with .NET for quick deployment of applications on workstations, and PHP for web development. I've never really seen any benefit of using .NET languages on the web when a great system is already there with PHP.