Many years ago I obtained an earlier version of this program on a computer magazine front cover CD. The version I've got includes these functions:
Bolt together a set of individual static gif files to make one animated gif file from them.
Edit an animated gif file to add or remove each frame, adjust the timing, etc.
Create a transparent gif file (one selected colour is transparent).
Edit a transparent gif file to select a different colour to be transparent.
It's also quite easy to use. Personally, I find GIMP extremely powerful and feature rich but utterly mysterious - but that's just my humble opinion. GIMP is more appropriate if you need to create graphics with layers (eg pictures with text captions), but I find creating graphics of that complexity much easier to do in Visual BASIC. I don't think GIMP can do animated GIF's but I might just never have found that option.
As a user of Photoshop, GIMP, and Paint, I'll say that GIMP makes a lot of sense only if you've used Paint before but not Photoshop. It does have a learning curve, but Photoshop's completely different. There is a way to do animated GIFs in Adobe Imageready(comes with Photoshop), but it's extremely complicated.
Personally, I use Microsoft GIF Animator, available at VersionTracker.