I pretty much only play WoW, so this review is from that perspective only. And for those of you looking at this from the same perspective, to give you an idea of the 'level' its used at we're at SSC/Eye.
This device makes it ever so easy to end the use of 'clicking' (using a mouse to click on toolbar icons) as you have, without having to move your hand at all, 11 buttons within reach of your middle 3 fingers with 3 buttons to your left for your little finger to press to equate to SHIFT, ALT and CTRL (or whatever you have bound your additional toolbars to). Your thumb then uses the analog hat to replace the WASD or Control Arrows. Then right under the Hat are 2 more buttons, once of which can be jump.
I actually take one of my little finger buttons to be TAB and 'just' have the main 11 keys with SHIFT and ALT alternates...a mere 33 bound keys. The other keys at the front I have mapped to the special function actions.
Result, all the regularly (and not so regularly) used abilities are within easy finger reach, and as a tank I can interspace Heroic Strike with the regular tanking abilties immediately the cooldown ends, and can react faster to hitting the required keys for example shield bash or Shield Reflect.
In short, this made my tanking life a lot lot easier.
Downsides - if you're left handed, this isnt going to work for you. Its completely designed for right-handed people. Also, Saitek aren't very good at supporting the product. You'll probably have to go to their website to get the correct drivers and software as the one provided on the disc wont work - check the forums for advice from the user base.
It takes a little getting used to controlling movement with the analog hat (you have to be pretty precise) and remembering where all those buttons are, but is worth investing in.