INCOMPATIBILITIES:

- The REJECT target has an '--reject-with admin-prohib' option which used
  with kernels that do not support it, will result in a plain DROP instead
  of REJECT.  Use with caution.
  Kernels that do support it:

- There are some issues related to upgrading from 1.2.x to 1.3.x on a system
  with dynamic ruleset changes during runtime. (Please see 
  https://bugzilla.netfilter.org/bugzilla/show_bug.cgi?id=334).
  After upgrading from 1.2 to 1.3, it suggest go do an iptables-save, then
  iptables-restore to ensure your dynamic rule changes continue to work.