Just remember Save your old bios and if possible have a spare PCI video card handy should you have a problem....the PCI card (I have a 1mb Trident ) will allow you to flash back to the old saved bios in the event you lose power during the flash etc etc
I believe Gigabyte has a new bios just released on there site for the Radeons they carry.. I believe it only fixes one thing if I can remember right.. if things are good with your card, don't chance messing with the bios..
alot of people are flashing the bios becuase they have an LE board, flashing to a retail bios will set the clocks to Retail specs ie:275/275 without them having to use a utility to do so.. however some find issues caused by the voltage being set to low on their card and they end up with artifacts.. The only other advantage of flashing is if there was something wrong with the original, a bug or flaw that when corrected would make your card run more stable..