I finally got my Nexus 4 last week, haven't quite had it a week yet, Christmas day will be a week. I was angry about the wait but I'm not anymore because the N4 is fantastic and was worth the wait.
It depends why you want an N4, it's a great looking phone, the screen looks amazing and the processor is super fast but otherwise most of the features ie. Jelly Bean will be the same as your Gnex.
The rumours circulating about the Motorola X are vague atm, sources aren't even sure if it'll be marketed as an " Android" phone. I'm not saying it's not going to be any good but most info on it atm is purely speculation.
I don't regret getting the N4, I paid £279 (GBP) for the 16GB and sold my S2 (still under contract) for £150 so paid just £129 for my N4. I can't complain at that.
I think you should go for it, if you still want a Moto X then sell the N4 closer to the release of the X....
EDIT- Personally I have no real experience of LG, I've heard all the talk on the net but I've also heard these same people stating the build quality on the N4 is great. I wouldn't let any pass failings from LG cloud your judgement.
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