Pros:

1. The paid versions are fairly cheap for a logo and you get multiple different formats included in the download.
2. Their wizard creates an easy to use experience, I think just about anyone could use it.
3. Not having design tools really focusses this on non-designers, which takes away some confusion when creating it.
4. Would probably be beneficial for a small project.
5. Nice that the preview you of your icon provides not only a simple icon but also some real-life examples of how it could look on your site.

Cons:

1. It doesn't have much customisation to allow you to make it your own and really personalise it to your company. This kind of contradicts pro 3 though.
2. The free options aren't very good and I would see you need to use a paid option to get the benefit of this product. Pro 1 compliments this though.