Radios are what control the cellular data of your phone, e.g. it's what enables your phone to make calls and send/receive data. Flashing a new radio is really the only way to brick your phone so proceed with caution. New radio updates have become available to provide fixes/enhancements such as signal strength, signal lock/switching. Stock Android radio I believe is ERE27. The newer leaked radio is ERE36B baseband version 4.03.00.21_2, the even newer leaked radio is ERE54B baseband 4.04.00.03_2.
I'm running the latest ERE54B radio and over the ERE36B radio I'm experiencing better 3g signal and it holds that signal better, I'm also been seeing about a 7% increase in battery life.
If you plan on upgrading your radio make sure to read the instructions carefull so you don't brick your phone. If you aren't much of a tinkerer or haven't rooted yet I'd suggest just sticking with the ota updates and wait for them to rollout the radio's.