There's some alternative to Flex, one of those is Laszlo.(http://www.laszlosystems.com/ and http://www.openlaszlo.org/)
Take a look at lzmail or dashboard. Both application have a strong design, and quite light more or less 700ko.
It's look realy intersting, best of all they publish spec of Digital Life webapp that could be a next step of media center softwares.
and finaly, check "how-to" demo here :
http://www.laszlosystems.com/lps/laszlo-in-ten-minutes/
