Re: What would be the gain with an Internet 2?
Whatever the gain, I strongly suspect it's not going to ever see fruition on a grand scale. It's been going since 1996 and still doesn't look like it's really gone anywhere (sure it's got some claims, but after 10 years I'd expect a lot more.)
Perhaps I'm missing something, but it seems most of what it claims to offer either exists at the moment but didn't really in 1996 (VPNs for example) or looks to address problems that don't really seem to exist on the level they're stating. I can see the benefits as Joga said of having a purely academic based network, but again we've kind of got this in the sense that anything on a .ac or .ac.xx domain can be considered academic and broadly troll-free.
Save the whales, feed the hungry, free the mallocs.