This is cool! Macromedia Flash 8 has introduced built-in support for downloading and uploading (with help of server side script) files with server. It is notable that the the player will be able to support uploading more than one file to the server, you can check out the worked out examples at Oniam Software Blog.
Advantage is that now displaying a progress of file upload will be easier. I am not sure if the post-back can be avoided with the help of asp.net 2, will have to check that out.