I use the original Logitech G15 gaming keyboard (18 keys, 3 M keys + MR key). I disable all the logitech software so I'm only utilizing IS/ISBoxer to configure my keys.
I use an X-Keys Desktop (20 keys) USB device to the left of my keyboard. Again, no software, all configured through ISBoxer.
I use the new Razr Naga, 12 keys for the keypad and your standard 5 buttons after that... This allows me easy access to ~50 keys and 5 mouse buttons, plus ctrl/alt/shift combo's as needed.
I think what would be useful is a discussion of simply what the goals are - you bring a lot of things up in your 'Possibilities' videos - the VFL thing for instance, which I get the gest of I'd still like to read/hear more about the general ideas behind it. I'd really like to see more detail in that regards.
My goals have changed a lot since I started multiboxing. I created my first "multi box" character as my priest. I had a 60 rogue, guild needed healers... so I started a priest. Around level 10 I realized how painful it was to try and do anything useful as a priest alone in the world... so I started driving around my rogue helping my priest. Started with a simple macro allowing me to /follow on command... I used Maximizer to display all windows at the same time but never setup a multicaster. I used some very complex macro's and a very hacked version of whispercast to build a UI mod that played the priest for me... all I had to do was tap a key on a 2nd keyboard and the priest would do what I wanted for the most part. That of course stopped working with 2.0 and all the changes made to the UI code - which was in all actuality a godsend for my multiboxing.
I was talking to a friend one day and commented "wouldn't it be great if I could send 1 keystroke to two clients running on the same PC?" I looked into it, and found KeyClone... within a short time I setup a 3rd account and was leveling my pally/mage/mage from level 1... I tried PVP when they got 70 but discovered the pally/mage/mage comp wasn't viable...
I tried switching to 5 shamans, I got level 30 by the time RAF released... then I scrapped all 5 shamans, bought 2 new accounts, and leveled a 4 box to 60, leveled a shaman with granted levels to 60, transfered him to a useful account, and I had 5 accounts... I'd switched to Innerspace by now, so had high hopes of being able to kick ass in Arenas... got the guys up to 70... formed a 5v5 and logged 4 in with a dedicated healer...
3 and 17... So it ends up I sucked at arena
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When Lich King released I leveled all 5 shamans because healers are easy to find groups for... my guild needed one, so we geared one... I needed one for pugs, so I geared another... I've got two with gearscores near 5k (one over, one under) now.
So ISBoxers gotten so cool that I'm not using any of it's real power doing 5x 1 class... I figured I'd wind up an old team... but I hate wiping so only take 4... I grabbed my original rogue, two mages to keep it SOMEWHAT simple, and the pally to tank. Motivations now are to hit 80 with them, gear them and be ready for 4.0 to drop. I've already got darkmoon cards for both trinkets on the mages and rogue, by the time they hit 80 I'll have Ulduar Belt/Boots and TOC Chest/Bracers crafted for all of them. I'll take all four through Naxx and TOC once and with a little luck I should be ready to roll some pretty serious heroic grinding after that...
Ultimately I'd like to be able to handle any encounter a normal party can. I believe that it can be done, between wow's robust UI and ISBoxers powerful toolset I havent' come across anything I can't yet. I even have a theory for how to handle a complex fight like Thaddius, but it involves writing a UI mod to manage following and at least 3 other players who know what you are doing and will work with you to position properly.
Fear sucks, but range on follow is pretty good, and being a shaman I have tremor down frequently.. normally I just run a loop and scoop them back up.