At the beginning of the preview (and some time before) I was thinking about shooting a barrel roll style synth but found it challenging to take photos at even increments of 'roll'.
I had anticipated that Photosynth would still find 'World Up' and would essentially stabilize the walk as the photos rotated around the center of the screen.
While skimming David's favorites, I found xarathion's test: http://photosynth.net/preview/view/6e636990-68e9-427b-911a-3c40469cc301
Instead I found that Photosynth 2 prefers to stick to 'Photo Up' even while playing the slideshow here.
I'm curious if this is because of the desire to fit the viewer to the input photos or simply because the photos taken at close to 'level' do not outnumber photos taken at other 'roll' values in any substantial way.