I have rooted a couple of previous phones, but in those cases there were exploits available to unlock the bootloaders on those phones so it did not affect the warranty status.
I guess this is a smart way for Motorola to do it - allowing people to easily unlock their bootloaders takes away most of the incentive for finding an exploit.
Still, if the phone develops a hardware problem that exists even after returning the phone to stock - shouldn't that still be covered by the warranty? I guess from Motorola's point of view, the user who unlocked the phone may have messed it up and Motorola shouldn't be responsible.
I bought my phone using a credit card that doubles my warranty up to an extra year so, in theory, I have two years of warranty. I suspect that the majority of phone failures are due to dropping the phone which would never be covered under warranty anyway. Square Trade insurance backs this up, at least for insured phones: "We next drilled down into the two main reported causes of accidents, drops and spills. Unsurprisingly, drops are responsible for most accidents – 77% to be precise"
I have seen threads where people sent money to a "Chinese middleman" in order to get an unlock code but I wonder - how do they know that the guy isn't just requesting the unlock codes from Motorola and violating their warranties at the same time? They wouldn't know unless they made a warranty claim, would they? Is there a way people can check on the Motorola site?
The stock experience on the Moto G is very good as are the updates - I currently have 4.4.3 and am hoping for 4.4.4 soon. And it seems to have been reported that we will even get android L when it comes out. From my forum reading, I get the impression that most people unlock and root their Moto G to be able to run xposed and make small tweaks to their phone. Which did you choose - warranty or root?