We are using Easy PDF with NAV 3.7B (5.0 client exe), and it works fine. It does what we want it to do.
We are currently upgrading to NAV2013, and our partners have been suggesting we move away from Easy PDF and invest in ZetaDocs instead (not Express version, mind you). They claim it does most of the same things. That's for you to decide. We are sticking with Easy PDF for now.