I hate to put a damper on the positive G303 posts, but I, too, picked up a G303, and thought the shape wasn't that bad and could be something I could get used to... at first. And then a couple of weeks into it, I just got tired of the shape and set it aside.
It's that weird diamond shape - causing me to have that more "forward" and "aggressive" claw/finger-tip grip. It just doesn't make sense, man.
I play D3 a lot, and the Demon Hunter class (an archer class, basically) is what I play the most, which requires a lot of kiting (not a lot of broad sweeping movements like when playing an FPS, but short and really quick movements). And the shape is just horrible for that kind of movement. My fingers and hand need to be stable to be able to make those moves, but those angles make it hard for me to keep a consistent grip while making those quick movements. My preference is definitely for more of a straighter, ambidextrous shape, like the Zowie FK1.
I honestly don't know what's going on in the Logitech offices over there. It's like they don't even do tests on their products, given how their latest products like the G303 and G502 have glaring usability issues (terrible shape on the G303, and the ridiculous weight on the G502) - it's like they just slap together a bunch of features, and call it a done product.