We have a requirement from a customer to provide a "lite" version for dial-up and all the bells-and-whistles for a broadband user.
The solution will use Flex / Flash / Java EJB and some jsp.
Is there a way for the web server to distinguish between the two?
You don't care about the user's connection type, you care about the download speed.
Have a tiny flash app that downloads the rest the of the flash, and times how long it takes. Or an HTML page that times how long an Ajax download takes.
If the download of the rich-featured app takes too long, have the initially downloaded stub page/flash redirect to the slow download page (or download the bare-bones flash app, or whatever).