Sometimes making the jump to the next version of Android introduces more cons than pros. This reality caused T-Mobile to pause and take a step back the last time it started to roll out Jelly Bean to the LG Optimus L9. Users complained of excessive battery drain and difficulty receiving calls, among other things. It's been a couple of months since that debacle, and now the carrier is ready to try again.
The update is up to 355.7MB in size depending on which version you're currently running. In addition to Jelly Bean, the update brings in the usual assortment of unspecified security enhancements. Since this is an over the air update, all you should have to invest in it is a stable WiFi connection and patience. The update has been rolling out for a few days now, so chime in if your experience has already gone smoothly for you.
Thanks, Andrew LeRoy.