Pros - No Trot!
Great smooth gait when moving out.
Cons - Different walkers gait differently. So much depends on breeding. Some have a nice slow walk like other horses, others are amblers with a huge overstride which can sling you back and forth in the saddle.
Sorry, don't have a video, I used to have a walker, but moved onto a different breed of gaited horse that has a much better gait for me.