I bought a spindle of G04 when I first got my 2500A, but had the same problems as many people with the G04. Hit and miss burns and even the "good" burns dropped off at the end (in cdspeed and dvdinfopro graphs). I stopped using them and switched to TY, which haven't given me any problems.
Reading about Herrie's latest firmwares, I decided to flash my drive and give the G04s another try.
I'm happy to report Herrie's 1.07b7 has solved the G04 issues for me. I burn at 4x and verify with Recordnow DX, then do a readspeed/error check with DVDInfo Pro. All my burns have consistenly been good, no errors and smooth read speed curves.
I haven't had a need to try Herrie's newer release, since 1.07b7 seems to work fine for me. (I am crossing my fingers for a dual-layer firmware someday though )