ClickOnce deployment enables you to deploy self-updating Windows and console applications that can be installed, updated, and run from a Web site. For more information, see ClickOnce Security and Deployment. In Visual Studio 2010, there are some small but useful improvements.
Starting in Visual Studio 2010, you can target .NET Framework 4 or multiple versions of the .NET Framework in your ClickOnce deployment. You can also troubleshoot installation issues by using enhanced logging and you can create a custom installer.
For Office solution developers, there are additional ClickOnce enhancements, such as deploying multiple Office solutions in a single ClickOnce installer and performing additional actions after the ClickOnce installer is finished.
For WPF XAML browser applications (XBAPs), you can request elevation of privileges with ClickOnce. For more information, see WPF XAML Browser Applications Overview.
I especially like the custom installer option. Now you can implement custom user experience during installation, including custom dialog boxes for security and maintenance operations.