Pros:
- simple and intuitive website for everyone
- allows you to create interesting and creative banners
- possibility to choose from variety of ready-made templates
- a wide range of output formats including movable (ie. HTML5 and gif) and static (png, jpeg)

Cons:
- not so many stock images to choose from and the viewing panel for them is much too small, making it difficult to search
- bottom bar which is used for editing moving objects isn't so intuitive
- exporting moving banners into static format is quite complicated

Overall It is a site where you can easily and quickly create inspirational banner ads without any experience. I highly recommend it!