Headphones and Surround Sound

I'm looking for a solid set of headphones to use on my PC. Basically I'll be using to listen to music while I work, and to watch movies and play games while my girlfriend sleeps. The more research I do the more features I see, and one thing that sounds really cool is the 3D Surround sound. How big of a difference does this make? I saw a few headphones at Frye's with SRS 3D Surround Sound but I couldn't test them out. Is this a worthwhile feature?

It's certainly not going to replace your surround speakers, but it's fun, especially if you play shoot-em-up games that make use of surround sound (nothing like hearing someone sneak up on you in Splinter Cell or who knows what in Resident Evil). That said, I would caution against paying a huge premium for this, it's fairly standard fare and has been around for years.