Something that hasn't been noted yet is that it is not easy to get the nuke cycle going effectively, and you have to put yourself at risk of attack to do it. The majority of nations launch zero to very few nukes all game, and most of the nations that do get a nuke cycle going can launch very few each year, and only launch as many as the most successful nukers when fed a bunch of credits (Turkey is a good example from this game). As an example of how difficult it is to get a strong nuke cycle going, consider that to launch 5 nukes/year consistently, you need an adjustment of +10. That's not including builds needed to increase range or place units on the board. To be +10, you're running a large nation with very few units. That's partly what happened with UK, and why he would have been ruined if his allies turned on him: he was wide open.
Even after nukes are up and running, it's still dangerous to use them to effectively stab someone. Sendric noted that the first attack on UK included 5 nukes from China, 3 from Mexico and 2 from France. The follow up attack was ~5 nukes, and I don't recall how that was split among the three nations. I see absolutely no problem with this - three nations, all with nuke capabilities of varying strength, teamed up to stab a larger nation. Importantly, these three nations, as a group, didn't have nuke cycles of 5, 3, and 2 nukes per year, respectively, but actually ramped up nuke production (and/or were fed credits, I can't recall) for a very strong initial stab. It's evident by the comparative weakness of the follow up. They expended all of their nukes and, at great risk, lowered their defenses and opened themselves up to a stab. It's a calculated risk that anyone attempting that sort of stab has to take.
A hypothetical involving the stab on UK by China, France and Mexico. It worked out amazingly well, but what if China had decided that what he really wanted was to be number one at that point, and he nuked Dario instead? 5 nukes hit UK to stunt him, 5 nukes hit France to largely take him out of contention, China potentially dodges the OL/Argentinian nukes. It's really risky even being involved in attacks like that.
In the two runs of NWO prior to this one, each had a different rule placed to attempt to limit nukes, and each backfired. The first had an "Armageddon rule", where 50 nukes were allowed to be launched - the 51st caused the game to end with no winners. Once we got to the point where nukes launched + nukes on the board was more than 50, a few players panicked and voted for everything to ensure the game would end with at least some winners. The result was entirely forgettable - I have no idea who won (but I do remember who the frontrunners were, and this was a game that Ling, for one, had a great shot at winning as USA). The second was last game that Rob G. noted, where we had a limit placed on nation ranks nuking nations of lower rank. I recall it was that a nation could nuke any power above their own, but only one lower - so UK rank B could only nuke ranks A, B, C powers, and a rank E and F nations could nuke anyone. The result was that F nations that developed strong nuke cycles and eliminated/befriended all E nations could blast the A, B, C, and D nations without any fear of reprisal, and that is what happened.
As of now, developing a very strong nuke cycle is not necessary for a win (see Sweden), and it does not prevent you from being knocked out (see UK, China). Having one helps tremendously in many ways, but it's very difficult to obtain and maintain, and even after you do have it, a lot of people that you interact with thinks you're bullying them because they're afraid that they're next in line if they disagree (or disobey), as I'm writing a bit about in my own EOG (it'll be up here some time).
I don't think that there should be any changes to nukes. There's this idea now that they're horribly overpowered because a handful of players each game utilize them very efficiently, and of those players, some are fortunate enough for things to work out in their favor (while the others aren't). I think it gives this false impression of how easy it is to get them and to use them once you have them.