Does it have _real_ subroutines?

About performance: the current version is missing some optimizations and is noticably slower than iptables with linear classification. I have a few optimization patches that inline small aligned data loads and comparisons into the main evaluation loop, which results in about equal performace to iptables (it can't be compared directly).

Where nftables gives better performance is when you're able to restructure your rulesets to make use of sets and jump and data maps to reduce the amount of rules evaluated for each packet. Sets are pretty obvious I guess, with jump maps you can structure your ruleset as a tree and have efficient classification in the nodes. Data maps allow you collaps similar rules than differ only in the target, f.i.:

iptables ... -i vlan0 -j SNAT --to-source ip1
...
iptables ... -i vlanN -j SNAT --to-source ipN

becomes

nft ... snat map meta iif { vlan0 => ip1, ..., vlanN => ipN }