~5 hours in: it's promising. Needs work, like literally every PDS game at launch, but it could definitely be great. Eventually.
It feels like a step backwards in some ways -- the map is very pretty, but the performance is awful (on a 7700k/1080ti). The UI is, if not ugly, at least unpolished: text overruns its columns and frequently overlaps. These are kind of minor complaints and I'm sure they'll be addressed in the first couple of patches. There are some great improvements, like being able to automate armies, which is a godsend for minor wars (who needs vassal swarms when you can just set a few legions to "independent action" and let them do their jobs?) and I hope it's a feature in every Clausewitz game going forward. The dynamic portraits are going to be awesome if/when PDS makes CK3. (And a CK map with the density of Imperator would be really amazing.)
It's definitely a map painter and even more focused on that than EU4. There is literally nothing to do during peacetime except click through and promote/assimilate pops (which is already unmanageable with 500 or so cities) but I'm hopeful this will be addressed with expansions. CK2 was also pretty barebones at launch (seriously, go watch some 1.0 Let's Plays) and EU4 only had content because it contained everything from EU3 + its expansions; Imperator seems to have borrowed only the ideas from EU: Rome and pretty much implemented everything from scratch. I guess the question is how long it'll take them to churn out improvements.
Most of all, what I want to see, is more *mechanics*. Flavor events are neat, new laws are kind of whatever, but the best CK expansions were the ones that added new dimensions of interaction, like Conclave and Way of Life. Condottiere from EU4 were also very fun. I'd like to see the Cursus Honorum implemented so you can't go making a 16 year old governor/general. "Make peacetime interesting" is also kind of important, because right now there's not much to do while you're, say, waiting for your manpower to tick back up. I have no idea how they'll fit that into the game design though.