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I got this as a gift quite awhile back and it just sat there for awhile because I was little intimidated by the thing. But recently I decided to give it a go and it's definitely a game-changer.
The biggest thing it does is it records macros and has way more keys within reach than on a normal keyboard.
For instance in PVP alot of people don't realize the importance of focus targetting. So I worked with it a bit and managed to get this with one key press:
target nearest friend + select target of target + take cover + activate bio stim + activate DPS boost + main attack
There's basically two ways to record a macro: select a macro key and just push the hotkey buttons in the sequence you want.. The other way is to record times between key presses. If the global cooldown is going to come in play you'll want to use the second option.
For soloing its great because you can control your companion better without spending extra time managing their attacks. You can set it up to where their attack target command is macroed to your main attack key. That way they're always attacking your target. You can also turn their AE autocast off and set it to where their AE always works in tandem with yours. No more watching them blaster sweep a big bunch of nothing.
If you're with a healer you can set up a hotkey for their CC, tab to the target you want on ice, hit the CC key and go about your business.
It also lets you name and save all of the macros and create profiles for all of your characters. I try to stick with as many of the same keys as possible but if you go from playing a healer to sniper you really need a profile saved for each character.