We currently use ABCpdf in one of our more complex applications. It has served us well and is not very expensive at all. I like that fact that I can send it raw HTML text and it will render it to a PDF in memory or as a file so we use to generate PDFs on the fly and serve them up via the web without actually ever saving it disk ever.
We have been using it for about 3 years and early on I had to use their support for a very odd issue that was very specific and the support was very fast and help solved the issue quickly.
You can find more information on their website at:
http://www.websupergoo.com/abcpdf-1.htm
