Barring a shareware style demo, I rarely make a leap of faith into a new software product. However, stellar reviews and/or at least a video example can make up for that. Maybe one exception would be updates to products I currently use.
I too have found myself watching videos of apps (particluarly games) before buying now if they don't have a free version.
I was actually considering doing an experiment where I removed some of my free versions of apps from the Market and put in better videos to see if I could get the same results.... I doubt it, but...
Barring a shareware style demo, I rarely make a leap of faith into a new software product. However, stellar reviews and/or at least a video example can make up for that. Maybe one exception would be updates to products I currently use.
[edited for clarity]