I am pasting below our previous response in addition to the info we have already provided in the FAQ
What are the limitations of the previous version that require an upgrade of your project? Is there anything we can help to address those?
RadControls for ASP.NET AJAX are our next-generation ASP.NET controls, which are built on top of the industry-standard Microsoft ASP.NET AJAX framework. The ASP.NET AJAX suite delivers faster performance, unified programming model and enhanced functionality. The benefits of the ASP.NET AJAX controls compared to the classic ASP.NET controls are summarized below:
- New client-side features, which are based on the underlying ASP.NET AJAX framework
- Faster performance due to the on-demand loading of scripts
- Simpler deployment as all controls are now shipped in a single assembly
- Unified programming model; learn one control and know them all
- Built on top of the industry-standard Microsoft ASP.NET AJAX framework
- Minimized memory leaks
- Common skins for all controls
- More controls, including tools that were never available in RadControls for ASP.NET, such as RadScheduler, RadColorPicker and RadSlider
For more details on the advantages of the ASP.NET AJAX controls, we invite your clients to visit: http://www.telerik.com/products/aspnet-ajax/why.aspx
Everyone who would like to take advantage of the performance optimizations and new features of the ASP.NET AJAX controls can upgrade their project. Please note, however, that Telerik will continue to support the classic ASP.NET controls until the end of 2010. Also, be advised that RadControls for ASP.NET AJAX are not backwards compatible with RadControls for ASP.NET.
Although the time for updating varies, depending on the size and complexity of the project, as well as on the experience of the developer involved, moving to the latest build would indeed require that you set some time aside. While for some products, such as RadAjax, the transition is going to be painless (see RadAjax for ASP.NET vs RadAjax for ASP.NET AJAX
), for other products, the migration will be more difficult due to the new architecture, use of single assembly, new API, and other changes introduced in RadControls for ASP.NET AJAX.
For every control we have a help topic dedicated to the upgrade from ASP.NET to ASP.NET AJAX version and the changes in the respective APIs. For example, this is the topic for RadGrid:
the Telerik team