Searchmash has been around for more than a year now, and their current UI has been written in Flex!
A few things that I noted:
Their data transfer with the search server is in JSON.
Google maps is being loaded on an iFrame over the SWF.
pretty cool. The only problem I see with this approach is, If a user right clicks on the SWF and selects the 'settings' option, he's pretty much stuck. Only way to get over it would be to refresh the page. This is because the Flash app pops up the settings modal window, and since the iframe sits above the flash app, the user can never interact with the settings window.
I like how they've integrated a video search tab - which searches for the video in google videos ( and hence, youtube) and loads the video player swf from the corresponding site. Simple, and neat.
Techcrunch isn't very thrilled about the app being Flash. They question 'why flash'; and I ask, 'why not?' I mean- searchmash is a site for experiments, isn't it?
The author of the techcrunch article wonders if Flash is as fast as AJAX, and quickly decides to assume its not! He should probably take a look at the benchmarks here
Searchmash also shows snapshots of the results , using snap.com's technology. Apparently, guys at snap.com are very thrilled about this: http://blog.snap.com/2007/10/25/breaking-major-news/