funny...if noone else answers then I' ll do it...
No, no special precautions to take except for these:
1. up to FOS 5.2, PPPoE or DHCP on any interface prevented HA clustering. In 5.2 this is allowed.
2. Especially with PPPoE you can enable to have the default (ISP' s) gateway assigned by the protocol. You should know that the metric for this default route is set in the interface page and not in the routing settings. Default is a distance of 5 which might be OK (at least I' ve never had to change it).
All the rest wouldn' t change, like policies etc. As for the special parameters for the PPPoE negotiations (PADT etc.) - I' d leave them at their defaults. Never had to change them.
You might want to enable DGD as with any other WAN interface.
One last, in my setups I always have a dumb modem in front of the FGT which is ' blank' (no user credentials whatsoever on it) and in ' pass-through' mode. This way, all information is in one spot, and if the customer later changes the access technology (e.g. from DSL to cable) then you only need to exchange the modem.
Ede Kernel panic: Aiee, killing interrupt handler!