I used to never use Nationhood at all, but with the new 25% Espionage bonus, I decided to try it out. Between that and Bureaucracy going to High, I noticed that when my empire is big enough, Nationhood is beneficial at that stage and Bureau is NOT. I habitually underbuild my army and got suddenly invaded by a couple SODs. They burned one of my little cities to the ground and gave me Musketmen as partisans (just got Gunpowder, didn't have any built yet). Those guys kicked some butt. But I still had the other SOD coming to a more important place, so I noticed I could draft, and did so since I was likely to lose the city anyway.
Before long, I was drafting Musketmen left and right, made short work of the invaders, and counterattacked with them. I couldn't have done this if I had relied on production, and whipping would've been too expensive, but each Musketman cost only 1 peep. The downside was that later, I discovered the cost went up, and I wasn't willing to pay it. (I RARELY whip units, only buildings.) So now, thanks to your post, I know where the boundary lies, and that the higher cost is justified, but I still might not utilize it.
As I played further games, I appreciated the money saved from Civics maintenance, and have drafted muskets and rifles a few times, particularly if it looks like I'm about to need them.
Drafting must be done with some sense, though. Don't do it in large production cities, do it in small, less developed cities where their economic and production impact and wastage of XP is minimal. I don't know if I'd keep on Nationalism for a long period, but it's a great thing to kick a Golden Age off for if you need some troops in a hurry, and your best time is right when you get muskets or rifles, ahead of anyone else.