Yep, there are those pesky techs and resources for nukes.
Nukes are not very cost-effective. It will hurt, but not nearly enough to justify the rep and pollution hit. Build a bunch of troops and deliver that to their doorstep to really make them squirm. Nothing else gives that gratuitous earth-shaking pummel, though.
I never build Manhattan, but use ICBM's for SS pre-builds if someone else builds it.
In Civ2 you had the delay from launch to SS victory in which nukes were a convienient to keep from getting wiped off the map.