Yes and no, it really depends on how his configuration is setup. If your running a true hardware setup (one WoW client per machine) then the Bigfoot Killer NICs wont really do anything for you unless the systems you have are hugely under spec, and then I would advise spending the money on some hardware upgrades that would far increase performance overall. If on the other hand you are running multiple instances of the WoW client on one machine then these NICs could be of use as they off load network processing from the CPU to their own NPU which will provide a small increase in network and computer performance.

I actually run two slave machines with two WoW clients per and I have Bigfoot Killer NICs in both. Both slaves are duel core with 8 gig of ram and symlinked data and interface directories, but I did notice a 20ms avg drop in ping after installing the Killer NICs. Having said that I do on rare occasions experience this very issue. These NICs are not going to fix issues to do with the network between your systems and the Blizzard servers.

As for the registry tweaking idea; I would take any such suggestion with a grain of salt. If your really concerned about it go into your router settings and disable QoS, or WMM as its known on some newer routers. Frankly its a security hole in some situations and due to its implementation requires applications to specifically trigger it so your likely getting no benefit from having it active anyway.

- Aldercy

EDIT: Just to note I only run the Killer NICs in my slave systems; my main rig which runs only one WoW client has a regular gigabit NIC in it and is perfectly stable. Also on board NICs tend to use the CPU for network processing, so even a standard PCI NIC could see some small improvement compared to on board.

EDIT 2: I also want to point out how stupid it is to download any script file from an unknown source, especially when posted on a World of Warcraft related forum. If I wanted to get a key logger into your system this is exactly the approach I would take.