Typically, everything supported in ASP.NET 2.0 versions is supported in ASP.NET 1.1 except for some framework specific functionality for example binding to declarative DataSource (which are only available in ASP.NET 2.0), design time smart tags, etc.
In the help of each control there is a section called "ASP.NET 2.0 features" section, for example for the grid:
This version of r.a.d.grid is complied against the
.NET 2.0 framework and offers new specific features for Microsoft's
next-generation IDE - Visual Studio .NET 2005. The new release will
enable developers to enjoy significant productivity gains, while
delivering feature-rich, standards-compliant, AJAX-enabled, and
cross-browser compatible web applications.
- More powerful VS.NET design-time support - the design-time functionality of r.a.d.grid
has been enhanced to support the new version of Visual Studio .NET
2005, along with its new productivity features like Smart Tags.
- Smart Tags - r.a.d.grid
takes advantage of the Smart Tags, which provide quick access to
commonly used configurations from a convenient panel right within the
design surface of Visual Studio .Net.
- Declarative DataSource support - using the Data access model in ASP.NET 2.0, the data access in r.a.d.grid for
.NET 2.0 can be accomplished in a declarative completely manner (no
code) using the new data-bound and data-source controls. They
significantly simplify the representation of different data back-ends
such as SQL databases, business objects, and XML files.
- Support for .NET 2.0 Themes - the
themes and skins features in ASP.NET 2.0 allow for easy customization
of controls appearance. You can define style information in a common
location called "Theme", and apply that style information globally to
pages or controls in your site. Just like Master Pages, Themes improve
the maintainability of your applications and eliminate the unnecessary
duplication of code for shared styles.
- Automatic Insert/Update/Delete in r.a.d.grid
With the release of r.a.d.controls for .NET 2.0,
telerik will be maintaining two separate versions - one for .NET 1.x
and one for .NET 2.0. The two versions will be identical in terms of
features except where mandated by the platform.