Im crew on the 777 for BA, They only fly it from LGW to BGI.
The only problem with the 777 is that the humidifiers are ineffective, the air is far drier and operating a long sector in it really dehydrates you. I have never felt ill on it or light headed. I know there were major problems at the beginning but I believe these have all been sorted out now and I have no reason to think otherwise after well over 2 hundred flights on the thing in the last 4 years!