For our company we experimented with using about a dozen animated GIFs - but found them to be a little hard to deal with. We replaced them with 2-3 short videos and were happier.

Now these product tours might be a good thing to add.

IMHO a 45-90 second video done right might the ideal medium for a product overview. But most are way longer, and suck, so I never click on them.

GIFs auto play, and so might be good medium to force a user to see a 7-15 second clip of how a feature works. Obviously you should ensure that only 1 is ever showed at a time.

I also find there's something hypnotic about a silently looping sped-up clip, though I don't know if this can be used to increase conversions. ;)

Yeah, we did not like the autoplay part and the hypnotic effects.