I attended a demo today from Cadac group showing Organice, a user friendly windows application for working with WSS sites. I think this is a good example of how to create a rich user experience using only standard SharePoint functionality.
From their website:

Ease of Use
Ease of use is a major part of user acceptance of any system. The Customizable user interface and easy grouping and filtering options make Organice the user friendly SharePoint experience.
Easy Navigation
The tree-based navigation offers a great advantage over the webbrowser. With Organice you can easily access frequently used SharePoint sites. Switching between several Sharepoint sites has never been so easy.

Viewing and Printing
The standard SharePoint interface does not provide any functionality to show the content of documents stored in the system. When a document is "clicked" the native application for the file type is launched. It would be too expensive for most organizations to have licenses for all users if they only need the application to view the content.
Organice has a built-in viewer that supports 240 different file formats. When a document is clicked the content is displayed in the "Property/Viewer" frame. Of course all documents can be printed this way as well.
Drag and Drop
Organice offers multiple select Drag- & Drop support for Document Libraries fom Oulook, Windows Explorer and between Document Libraries. Meta-data can automatically be copied when documents are imported saving valuable time.
Searching
Full-text search for meta-data is a feature only supported by Microsoft when Sharepoint is installed in conjunction with SQL Server. Organice offers full-text search for meta-data even when Sharepoint is installed on a standard WMSDE database.
Customization
In some cases additional custom functionality is required to implement specific workflow or back-office integration. Organice has a complete API to develop this functionality as extensions to the standard Organice program. Cadac Group provides several programming templates to make this task even easier.
The deployment of these extensions is as simple as dropping them in the Organice programdirectory, and they will automatically be loaded.
Multiple Document Templates
In Sharepoint users can only use one template per Document Library whereas a Document Library can contain multiple file-types. With Organice you can manage your templates (Companywide as well as project-specific) within Sharepoint sites. When a user creates a document he can select a template from all available company- of project-templates.
Document Automation
The meta-data associated with a document offers a great basis for document automation. Out-of-the-box Office integration Microsoft offers however is too limited.
The Organice Office add-in makes it possible to retrieve meta-data from Document Libraries and other related list-items to be used in Office Documents.
For Example: Simply by selecting a contact from a contact list in a meta-data field is enough to retrieve all address information from the contact list to be used in the document.
AutoCad Integration
The AutoCad add-in for Organice offers CAD users the ability to open/save, check-in/check-out and edit meta-data for Autocad drawings stored in Sharepoint sites within Autocad. XREF's stored in Sharepoint are automatically resolved.