SILLA  VectorDesigner is fun and easy to use, and the developer was very quick to answer my emails about bugs and feature requests. I saw some complaints in previous reviews about bugs with the layers, image fill, shadows, etc. - in this version (1.2) they have been fixed.

I recommend VectorDesigner to anyone looking for a fun, simple and intuitive vector application. The Flickr browser is pure genius, and the raster to vector conversion very useful. It's also fun to play around with the iSight integration and effects, and convert them to vector.  
(Version 1.2)