Since animating in PS is such a chore, I've written a program which loads my current sprite sheet and displays the animation. I run it in a separate window and just refresh when I've made some changes to the figures.
I suppose I could upload it, the problem is that all the values and file names are hard coded. Perhaps people could use it if I made a simple GUI for setting BG color, frame width and height, start and end frame, and frame delay.
But perhaps people require more features than that... such as chaining animations together so preview how a walk, run, jump looks.