Pivot is timeline-based, so on each new frame in your timeline you can move and rotate your stick figures at the various axis points to create movement. It'll leave a nifty outline of the previous position for comparison, which helps with in-betweening and smoothing out your motion. Hit "Play" and it'll loop your animation to let you see how it looks.
It's not hard to add new figures to your scene; you can populate it with as many stick figures as you want from the preset figure type (rather like Flash instances), or use the editor to create new figure types and litter your scene with them. The editor is very basic, but considering we're working with stick figures here, the ability to change the color of the stick figures alone is practically an upgrade.
You can also change scene size, and add a background image as long as it's a bitmap. The scene size will conveniently resize to the size of the bitmap image you've imported for your background.
Export options allow you to save as an animated GIF.
The interface is clunky and basic - pretty much your standard ugly "the buttons are there, what more do you need?" layout with no thought put into GUI design or user-friendliness. While in some ways that simplicity works in its favor, it's possible to do simplicity with elegance. Then again - freeware. There's always that to keep in mind.
You can't import sound, so if you do want to add sound effects, vocals, or a music track, you'll have to take it into another program - which may make you wonder what the point is, when you could have done all this in the other program in the first place.
You also can't export to Flash, which is a real handicap. Most people use Flash SWF or FLV format for videos they intend to share to the web, and the limitations with a GIF - both in color and the exorbitant size of the files - makes output almost pointless. The workaround is to export as a series of bitmaps and then import into Flash, which is just a pain.
The biggest peeve, I'd say, is the annoyance involved in creating and editing new frames. There's a Next Frame button that lets you add a new frame, and you'd think the simple way to edit that frame would be to click on it in the timeline, make whatever changes you want, then move on to another frame or go back to edit a previous frame. The thing is, it doesn't always work that way. Edit the frame, click elsewhere...and the edits haven't saved at all. It only seems to save if you click Next Frame in a particular set of circumstances, and sometimes this causes duplicate frames. It's not very intuitive or user-friendly.