With the caveat that I don't have a lot of experience with the iPad's pdf support I'd say the Fire's support is solid. I recently read an entire e-book in pdf format on it. The main limitation is that there isn't a lot of screen real estate so if you want to read it on a full page scale you need to tolerate a very small font (this was not a problem for me). A cool upside is that when you get a Fire, Amazon creates an email address that you can send emails with attached pdfs and documents which will then automatically be downloaded onto your Kindle.

Overall nothing mind blowing but if you like e-readers I think you'll be satisfied with the pdf support.