The best thing about this component is it's object model. It's rich and flexible. I can layout my documents in XML and add custom paragraphs with dynamic data from my own code. The XML thing saves me writing piles of stupid code to setup fonts, colors etc. It's almost as easy as building web pages :)
The documentation is pretty good, lots of samples available online and support is among the best I've encountered so far.
By far the best API for generating PDF in my opinion.