For those that missed the announcement last week, PhotoSynth is live and after a pretty bumpy start looks like you can at least play around with it now.  I've managed to load two of my sets of photos from a trip to the High Sierras a couple of years ago.  It definitely still has its bumps as I had to cancel and restart the synth several times as it would hang indefinitely.  I didn't get really high "synthy" scores as I wasn't taking the photos with PhotoSynth in mind at the time.  However, the PhotoSynth team has supplied a document of points to keep in mind while shooting photos if you intend to make a PhotoSynth out of them.  I can't wait to try it out when I actually shot the photos for synthing.  There are numerous really great examples on the PhotoSynth site, including some shot by the National Geographic Society photographers.  I like that you can go full screen (or full browser) as that really helps make the experience a bit more of an immersive experience.  Also, the slide show and thumbnails really help as well. 

PhotoSynth is now giving 20GB (!) for free to anyone to try PhotoSynth.  It takes a LONG time to use 20GB in JPEGS!  Give it a try. 

Since my photos didn't all relate to one another, PhotoSynth sort of creates mini-PhotoSynths inside each.  You'll want to check the thumbnails page to see the various scenes that it stitched together. 

Here are links to my first two:

High Sierras - Dana Plateau

High Sierras - Saddlebag Lake Area