If you take a look on
the Kobo forum you can find directions on how to install alternative readers on a Kobo. If PDF reflow is important to you (due to a large number of PDF novels) one of those readers will probably suit your needs quite well.
I own an Aura HD, and absolutely love it. I find it comfortable to hold, and excellent to read on. Kobo's defaults seem to work very well for me, but if you like to tweak your reading settings, the e-reader will accommodate you.
I would recommend the Aura HD's successor, the Aura H2O. For $10 more you get a newer Carta screen along with water- & dust-proofing.