I personally use the Roccat Kave Solid 5.1 as a Headset and I'm very happy with it for many reasons. First of, and most importantly, it is a true 5.1 Headset. The Logitech G35 and the likes all have only simulated Sorround Sound, which doesn't come close to what you get with this headset. It is very comfortable, lighter than the G35 and the biggest advantage to the G35, it is very durable. Don't get me wrong, I loved my G35, but the cable would break after 6-7 months three times and I was just tired of sending it back every half year. Maybe it's just my bad luck, but the way the cable is build, it seems it kinda.. "breaks" itself. I don't know how to really describe it with my limited English..
Back to the Roccat Kave, the sound is amazing, IF, and thats a big point, you have hardware that is adequate. Obviously, you need a 5.1 souncard that can support the real 5.1 sound, so it's not as easy as simple Plug&Play, you'll also have to fiddle the settings around a bit to find out what is your favourite setting. But it comes with a handy Desktop Remote with wich you can change the most basic settings quickly.
If thats nothing for you, I can also only recommend the G35, it's a great Headset. Even better, take the G930, the wireless version, which is great for more comfort, even though I can't really tell you how long the battery lasts, so recharging could be an issue. And if you get it.. Please don't be one of those guys that go to toilet with it, and the mic still on. It's really irritating being in Teamspeak and hearing a toilet flush.