The UseCompatibleTextRendering property is intended to provide visual compatibility between Windows Forms controls that render text using the TextRenderer class and .NET Framework 1.0 and .NET Framework 1.1 applications that perform custom text rendering using the Graphics class. In most cases, if your application is not being upgraded from .NET Framework 1.0 or .NET Framework 1.1, it is recommended that you leave UseCompatibleTextRendering set to the default value of false.
The GDI based TextRenderer class was introduced in the .NET Framework 2.0 to improve performance, make text look better, and improve support for international fonts. In earlier versions of the .NET Framework, the GDI+ based Graphics class was used to perform all text rendering. GDI calculates character spacing and word wrapping differently from GDI+. In a Windows Forms application that uses the Graphics class to render text, this could cause the text for controls that use TextRenderer to appear different from the other text in the application. To resolve this incompatibility, you can set the UseCompatibleTextRendering property to true for a specific control. To set UseCompatibleTextRendering to true for all supported controls in the application, call the Application..::.SetCompatibleTextRenderingDefault method with a parameter of true.