Hi Greg Duffield,
We are well aware of the RadGridView performance issues and dealing with this is our priority number one. Currently we are working on refactoring our UI virtualization and to be more specific on adding a horizontal virtualization of the grid columns. Also we plan to introduce a container reuse and recycling for further improving the grid performance as well as the memory footprint. This is a tough task since the new virtualizing logic requires a lot of changes and fine tuning for the existing one so at the end the result would be the expected fast performance.
We plan to introduce the new UI virtualization with our 2009 Q3 release which is expected in November. We keep high hopes that we will succeed in delivering a beta version of our controls in October.
the Telerik team