NS1 was a fantastic mod.
I'm a little disappointed that this isn't being hosted by Steam though. Natural Selection was a pretty huge part of the Half-Life multiplayer scene.
Hopefully they give Steam activation keys to people who preorder, since it'll most likely be a part of Steam once its released.
EDIT: I'm seriously considering preordering this...
Though I'd feel more comfortable doing that if we had some screenshots and gameplay videos.