Best method to obfuscate or secure .Net assemblies

This is a pretty good list of obfuscators from Visual Studio Marketplace Obfuscators

• ArmDot
• Crypto Obfuscator
• Demeanor for .NET
• DeployLX CodeVeil
• Dotfuscator .NET Obfuscator
• Semantic Designs: C# Source Code Obfuscator
• Smartassembly
• Spices.Net
• Xenocode Postbuild 2006
• .NET Reactor

I have not observed any performance issues when obfuscating my code. If your just sending text basted stack traces you might have a problem translating the method names.