hello. We need the route-to and reply-to functionality in pf(4) in order to support our service model. I was told this hasn't been implemented in npf(4). Also, the instrumentation afforded by pfctl(8) with regard to looking at state and rule tables seems to be pretty much non-existent under npf(4). We could probably live without that, but it's sure nice to have when debugging issues, especially when examining protocols that punch dynamic holes through firewalls.
-thanks -Brian