The G3 should have shipped with a similar sized battery! I really like my G3 (coning from an S3) but the stock battery life was appalling! I use my phone a lot daily for internet so screen on time is essential. I had a Lemon in my S3 and even with heavy use I could get two days.
So imagine coming from that to the G3 - I was constantly looking for opportunities to charge my phone at every opportunity. Even though the stock battery is some 3000mAh the battery drain really does render the device unusable (unpractical, at least).
I've had the 6000mAh battery now for a couple of days, and can finally not have to charge the darn phone all the time! The increased thickness provides better grip. I did have the Unicorn Beetle tough case on the stock device but, needless to say, that is now defunct. I coyldn't get hold of the case that fits this extended battery back but TBH it looks a but flimsy anyway. I've got a Lemon on order as my phones tend to take some punishment, and I don't give a hoot if it looks or feels like a brick. For me, a tool has just has to perform, and rubbish battery is not acceptable.
For those looking to rid their battery life woes, I'd say that this battery (in it's many branded and unbrabded forms) is a no brainer must have. It doesn't add a detrimental amount of bulk (like the Lemon) - it actually adds beneficial bulk. The only downside is a serious lack of protective case options - i.e. one!