You totally just necroed this thread, but what the heck
1. you can nuke the space operations of you enemy nations
You don't need nukes or anything else in space to do that: http://www.boston.com/news/world/asia/articles/2007/01/19/china_shoots_down_satellite_drawing_protests_worldwide/
2. you can bombard an enemy country with kinetic tactical nukes(rods of god program, large microfiber reinfoced beams)
How is that any different from just nuking them? And the name of the program was Project Thor, rods from god is just a nickname.
3. you can bombard enemies with nukes virtually undetected, compared to land based launching
Does it matter? When a city gets vaporized, whether from a nuke from land or space, it's going to be pretty obvious. An attack like that isn't going to remain a "secret" for very long. How many countries can put nukes in space? US, Russia, China... And someone might notice an unanounced rocket launch.
4. you can target any country, anywhere, any time, with less cost and less resources
You can already target any country, anywhere, any time. And putting a couple hundreds-of-pounds-tugsten-rods and a mechnaism for launching them would not be cheap. And why bother putting nukes in space when we have plenty of (cheaper) alternatives that require no R&D or additional infastructure?