At my first job, our most senior developer and my mentor was huge on Flex and instant it was going to be the next big thing.

At the time I thought it was inflexible to style and felt very non-native.

To be fair, it had its moment, moreso in desktop applications than on the web. I seem to remember a lot of installers being developed in Flex. The iPhone showed up just in time to kill it before it ever got its footing on the web.