i didnt even need the hotfix. i did it in vista 64 exactly like it says and it worked perfectly. the hotfix is for after you do it if it didnt work for some reason i think.

The behavior of TCP acknowledgments (ACKs) does not change after you modify the TcpAckFrequency registry entry in Windows Vista
that from the hotfix's website so it seems as though its a back up in case the registry edit didnt have any effect. but like i said i didnt even need it. i dont even think i had to reboot i saw results immediatly. im not big on registry edits it scares me everytime i open that thing but this one seems to be a pretty minor one. ultimatley its your call im just saying it does have an effect. im running all 5 clients at 45ms pretty much constantly now. back when i only played one character in never saw latency below 100ms so it did do something.

p.s. always backup the registry. i know its a no-brainer but thought id throw a reminder out there.