If I was planning to do that simple of a download control i wouldnt request one :)
1. Im thinking more of the lines of Serving Files that are located Outside the website...
2. Ability to download dynmic content
3. Ability to download Large files like 3GB files with Resuming capabilities
4. Ability to generate a Link if the download doesnt start automatically.
A Sample can be seen here from a previous ASP.net Controls suite i use to use. They have some very useful controls that i would love to see Telerik start to offer as i believe your developers can take even their concept of controls to a new idea..