As a strategy game, it's wondrous; as a piece of software, I'm finding it to be problematic. The gameplay is deep; running through a year of wartime often requires dropping the speed several steps. Taking care to keep forces equipped with the latest weaponry and in supply range is difficult, but nowhere near impossible; if anything, it's almost pleasing to be both general and logistician.
The real issue, however, is stability. It's rare to be able to complete a whole game in one sitting, even as a neutral power that never gets involved in a war. Particularly when playing a major power, the game is unstable and prone to crashing. Monthly autosaves alleviate some of the frustration, but long load-times compound the problem and rob it of some of the entertainment value. The fun is bulletproof, but only so long as it remains stable.
Crusader Kings II might prove to be a better option for someone looking for a general strategy game; Hearts of Iron IV is listed as in-development, so I might consider that a better option if it turns out to be stable.