I have not used one, but there are several small mini-usb batteries/chargers for sale at the usual web sites. If having spare batteries is a high priority, no need to consider this phone. Yes, there are some limitations/drawbacks to the Nexus 4 -- the biggest being the no SD card slot, and the sealed battery. I find these to be minor considerations, as I have never had a spare battery for any of my smart phones and I don't use my phone as a media center -- 16GB of storage is as much as I will need over the lifetime of this device.
Here are the primary advantages of the Nexus 4:
1. Bang for the buck -- for $400 (including T&S) I don't think you will find a better phone. At T-Mobile, I will save $240 plus tax over my two year contract by bringing my own phone. Or, I can choose not to have a contract, and leave my provider at any time, without penalty.
2. It will always get the latest Android OS updates immediately, without the added crap from either the phone manufacturer or cell provider. How many phones will get the current Jelly Bean OS, let alone the next one?
3. Free tethering and wi-fi hotspot -- no locking of phone to prevent using it just like any other computer. Full use of Android's capabilities.
4. Support and Warranty Service from Google -- I'm taking a leap of faith here, but who is happy with cell phone provider support, these days.