Thanks for the advice about Costco/Verizon. I looked into it and was faced with the most ridiculous, convoluted story ever...
Regarding the warranty exchange through a VZW store, it's correct that I can do this, just not right now. Apparently when you're still in VZW's trial period, they process every exchange as a store exchange rather than a warranty exchange, even if the phone is defective. So since I didn't buy it at Verizon, I can't return it to them, and I can't get the warranty exchange until after 1/9, when their extended holiday return period is over.
Also regarding the warranty exchange, you get a "certified pre-owned" phone rather than a new model. I'm not sure how that's really different for a 2 week-old phone, but so be it. I would rather have a new phone than a pre-owned one since I paid for a new phone, but it's not that big of a deal, especially if I can get better speaker volume.
Verizon actually recommended returning the phone to Costco today and then re-buying it from their corporate store (surprise, surprise...). I checked this out, and here's the really frustrating part. I've owned this phone for 15 days. Costco has a 90-day exchange period during which I can exchange it for the same phone or a different model (e.g. Droid RAZR). However, I found out today that their return period if you just take back the phone and don't get a new one is only 14 days. After 14 days, they can't (won't?) reverse your new contract to make you eligible to buy the phone again from some other vendor. So here I am on Day 15, and I can't return the phone to Costco without completely getting screwed over for buying a new phone.
So here I am unable to return it to Costco or exchange it for a new one (because every single Costco in my area is sold out). I even called all the Costcos in the area where I'm going to be spending New Year's weekend (in another state). All gone and none of them know when they're going to get it back. My options now are:
(1) Buy another phone (e.g. Droid RAZR) at Costco, then either keep it if I like it or exchange it again once the Nexus comes back in.
(2) Keep this phone until 1/9 and bring it into VZW for a warranty exchange.
(3) Keep this phone until Costco gets the new Nexus, then finally exchange it.
Or instead of living with a defective phone, I could just switch back to my trusty OG Droid. Right now I'm just using the phone with Bluetooth and headphones, but if something gets worse, I'll do that.
Kinda ironic that the supposedly benefical extended holiday return period is screwing me over at VZW, while its nonexistence at Costco means I can't return my phone today. This would have been a good thing for Costco to tell me 2 days ago when I originally went in to ask about the audio problem.
Very promising that your speaker volume is better, though! Is the battery life about the same?