'Guns don't kill aliens, i kill aliens' - Duke Nukem
As a Duke Nukem fan i enjoyed a lot that add-on, it's among my favourites, nice levels with some exception and new textures and sprites greatly integrated into the overall, all this makes Duke it out in D.C.
The last levels are really neat, especially Capitol Punishment.
Also the ending with Bill Clinton was funny.
Well, i find the Smithsonian and FBI levels kind of cheap, they look like a lot to thousands of mundane amateur levels hanging around the internet.
The other bad things are: No new music, no new monsters and no new weapons. If Sunstorm had taken a bit more of time on this, 'Duke it out' could have been a perfect add-on.
The Bottom Line
I would recommend it to Duke fans only, that is, more alien-ass to kick (although there are no chicks on this add-on...)