I'd like to point out and save some people the trouble of trying to set up the Hammer version in the Source SDK for NS. All our individual experiments in setting it up failed. For a version that works, I think we'd all recomend
Hammer Editor 3.4. The good news is that you don't have to run steam to run this like you do with the Source SDK, and the glitch were you scroll in the 2D views unsmoothly is not present in this version.
The bad news is is that it's not set up for any game, period. I'll be working on a tutorial to help those set 3.4 up to get it working for NS, hopefully done by the end of this weekend. I do plan on using screen shots, and will post a link here as soon as I can.
-Sirusblk