Ever since updating to 4.2.x, I've noticed my phone will do this thing where if I spend a decent amount of time out of service, my 3G connectivity won't come back (ever) until a reboot. This morning after seeing a thread about slowdown on 4.2.2 GNex I decided to take a look and see what could be done.
For what it's worth, my phone is pretty much "back to normal" after reverting the changes made in 4.2.2 - I had noticed immense slowdown on my phone, but had attributed it more to the fact that I've got a ton of shit installed more than 4.2.2. After applying the changes to boot.prop and rebooting, my phone no longer stuffs around on certain things like switching to Chrome. I was skeptical at first, as the "lag fix" thing sounded great in theory but turned out to be a bunch of hokum, but this has actually helped immensely in my phone's usage and Google have since marked the issue as a defect, so we'll see.
Anyway, after poking around a bit I realized that one of the Takju updates from Google had clobbered the Telstra radio I'd installed - I was on XXLJ1 (Europe, October 2012) . I haven't in the past noticed any problems using the US radios - however when I had to send my phone back to Samsung, it appears as though one of the first things they did was flash the Telstra radio back, which I then left. I tend to leave well enough alone as long as the phone doesn't have any issues, which is why I didn't notice I'm on the euro one.
I downloaded a dump for DVLH1 (Australia, August 2012) and flashed it with fastboot. It's still far too early to tell if it will be an improvement or not, but I wanted to note what I did and when in case it causes me further issues.
Update 2013-04-28: At the risk of jinxing it, so far so good. I may even have improved signal - I'm not sure about it, but I seem to have very good reliability getting SMS messages at my desk, which I normally don't have.