Users of LG Optimus G from Sprint with the model number LS970 can now upgrade their devices from Android 4.0.4 Ice Cream Sandwich to the new Android 4.1.2 Jelly Bean (LS970ZVB).
The Sprint LG Optimus G users can install the latest firmware update on their handsets through over the air (OTA) update. In addition, for those who prefer a manual installation, there is a way of doing that as well.
You can find the manual installation procedure on XDA forum now.
Update:
The Jelly Bean official update has not officially launched. LG states there was a leak, and the real OTA is still in testing with Sprint as of 02/28. Only manual updaters using the leak are using ZVB-01.
LG Optimus G Phone Photos - LG Cell Phone Pictures

MetroPCS has launched a new mid-range Android smartphone called the LG Spirit 4G, code name MS870. It runs Android 4.0.4 Ice Cream Sandwich, has a beautiful 4.5″ ture color IPS display with 960 x 540 pixels. Full specs include:
LG Mach Full Specifications:
MetroPCS LG Spirit 4G Phone Photos - LG Cell Phone Pictures

Sprint has launched a new mid-range Android smartphone called the LG Mach. It runs Android 4.0.4 Ice Cream Sandwich, has a 4.0-inch display with 480 x 800 pixels. Full specs include:
LG Mach Full Specifications:
Sprint LG Mach Phone Photos - LG Cell Phone Pictures