Let me say first that my experience with BannerBoo is very limited. Here are my finding from quickly trying out a few samples:

What I like:
- great job on the UI/UX overall.
- the strongpoint is the sample templates which are quite good and a good variety. I do hope that it will continue to grow weekly/monthly.
- I see the value in being able to quickly create some simple animated ads. Time is a big deal.
- I like the UI/UX more than Google Web Designer actually. Love the preview feature.

What I found lacking and room for improvement:

- the animation options seem to be limited mostly to in, out transitions. There is a custom animation option but that is not usable for what I tried to achieve. Can't seem to be able to simply animate by manipulating the item and add keyframes for rotation, size, colour, (css transform, translate, style) changes.

- the included object library is limited to a few items and limited functionality. Currently the templates are the main value.

- can't seem to be able to do animations like in Animatron: like creating/editing animating objects. For example, you can't create something like the animated snowman from one of the templates by animating the hand and the hat in the app. You'd have to bring a fully animated graphic in, therefor having to add another software in the workflow, which would no longer be as quick and simple.

NOTE for the developer: if you decide to add more advance controls, consider adding a separate toggle-able expert/standard mode. This way in standard mode the UI would remain clean and simple to use. Animatron has something like that.

Currently I'm still on the fence about it. I will play more with it and closely watch the development in the next few weeks and I will decide then.

However, the work that the developer has done so far is of high quality, and it deserves a high ratting. I think anyone interested in something like this, should give it a try and see how it meets their particular expectations.