I wrote this on a similar thread on SD.net, so here are my 2 cents...
I bought these headphones when they were released. I played through all of Batman AA with these g35s. The sound is pretty good, but at times, the 7.1 sound felt like I was in hall. You know that hall/big empty room setting you can adjust on virtually all audio systems? Kinda sounded like that for me at times. For some reason, when it was switched to stereo mode, it didn't suffer from the echo effect of a hall. Not many settings you can adjust from what I saw when I installed the logitech program either.
The thing I hated the most about these headphones was just how tight it was around my noggin. Even at the highest fit, I literally had to take them off every hour or so to relieve the pressure the headphones caused to my ears. Of course, everyone's head is different, so this is subjective. On a side note, the ear-cups are very comfortable, just the squeeze ruined it for me.
Ended up returning them after a week. I could have dealt or gotten used to the hall-like sound, but not the pressure of the headphones. I really wanted to like these headphones, but I'll wait for the inevitable g35 v2. Sticking with my cheap stereo headphones until then.