4G will suck your battery dry..if you let it.
Well not entirely true, but I live on the edge of 3G/4G coverage and my phone will go between 3g/4g/1RTT on a whim, and when it starts doing that my battery turns into a torch (funny--it really gets hot), and say goodbye 50% battery in an hour, gone. I have a t-bolt which recent UI upgrades are great, switching between technologies is not. If I force 3G it can run for 2+days, 4G it's a Vegas slot machine.
So I just leave my phone in 3G mode, because I can't take the chance that driving around in Boston or NYC I am going to get my battery drained, or it goes into RTT mode for 30 minutes.
When the 4G network is on, it's on and works great, but I feel like one bad tower or handoff and I'm done. My phone is not a toy, its my office. VZW deployment is half-baked at this point, or at least my phone. Either way its not reliable.
I'm also grandfathered, so I don't worry about data, although I use about 500Mb/month (use wifi when I can). I think the VZW tether charge is a joke tho, and they beg people to circumvent that.
3G is fast enough for me, however I bought a 4G phone and shouldn't have to deal with obvious carrier issues. With that VZW is apathetic to the issue, because they can't say they actually have a problem. When I first got the tbolt, I would have to charge it 2x a day, so software updates have helped.
With that I also knew I was getting the first 4G phone, and it wouldn't be ready for prime time which is sad, because we are all treated like beta testers these days...