Yes, I use HotKeyNet. You'll need to adjust the ClickMouse settings to get the most reliable broadcasting. Mine currently uses 3, 3 but I've also used 25 25 and 15 15 depending on how much of a strain mutliboxing is on my system.

You'll also need to make sure you are running all windows in the same resolution, even if they are all resized to different sizes. And for WoW itself, you need to make sure your UI Scale in game is set the same on everyone. You can edit that in game, which is sort of accurate, but I edited the Config.WTF. It's the one @ World of Warcraft/WTF/Config.wtf

Code:
SET uiScale "0.89999997615814"
But like I said, it is accurate enough for me to fish on all 5 guys at the same time and I have been using it for healing and AOE since Wrath. I also use it for things like gathering. The mouse broadcasting is actually why I started using HotKeyNet and stopped using Keyclone.