Lately I wanted to create short animations for my website. Nothing fancy, just about 100 frames with some sound effects. I'm far from a professional but just good enough to doodle some small clips. I tried to use my laptop to create those frames to eventually re-encode them into a movie clip, but it has proven a bit harder than expected. Not the re-encoding, but simply drawing each frame. Using a mouse to draw is not as easy as a stylus. I do have a Bamboo tablet but I looked into the AppStore to see what was available as the iPad is great for such task...
I finally made my choice on Animation Creator HD. At 1.99$ it is cheap and has all the features that I wanted. There is a lot of apps doing the same thing, but I wanted something simple to use. And this one is perfect!
Drawing tools are quite diverse, many brushes, settings and so on... The possibility to have layers was a big plus for me and even if I'm using the iPad 1, it works really well. Encoding a movie of 120 frames takes about 1-2 minutes so it's fast enough for me.
I do have some crashes from time to time, as I do with other apps on my iPad. So I cannot say that it has issues specifically. Only thing missing is the possibility to import an audio sample. You can only record via the microphone your audio samples for now. I had a talk with the developers and they are currently working on this feature for another release.
If you're looking for an animation app that is easy to use, Animation Creator HD is a good choice.