I purchased this device a short while ago in the hopes that it would sharpen my game up a little - I play World of Warcraft with a guild that is constantly chasing down hard-mode PvE achievements and I also like to engage in a spot of PvP once in a while, so the ability to move quickly, shoot while moving, and generally react instantly to the changing environment is crucial.
This is a fantastic device for my purposes, and I would rate it as the #2 item that every WoW player simply must have. (#1 being a Blizzard authenticator, for obvious reasons...)
The thumb joystick works well, and lets me easily move while shooting while using the mouse to control where I'm looking - its angle to my hand while on the device still feels a bit off after a few weeks of playing, and that is pretty much the only improvement I would suggest for the device, except that it would be nice if the software for the G13 and G19 keyboard could also be used to control my G9 mouse profiles. A 10-15 degree clockwise adjustment would probably make it perfectly angled for my hand.
Note: It takes some time to get used to the unit and the key layouts you decide upon. Don't try taking this into a raid or arena on the same day you purchase it - give it some time until you can find your keybound abilities without fumbling about.
Also, take the time to devise a number of macros either in-game or in the device control panel. It really is worth it when you start using the Logitech macro utility with any keybound abilities you have. Think shot rotations, think GCD wait times built into macros, think awesome-sauce!
Awesome device. I had a Nostromo and just couldn't get to love it. Different story with the G13, if you took it away from me today I wouldn't be able to raid.