Good : For those who have played Europa Universalis before, the interface isn't so frightening.
1) Historical Depth
2) Good Background Music
3) Better graphics than EU3
Bad :
1) For those who played EU3, and remember how getting 100K + of manpower was a tremendous accomplishment which could be done only by a very large nation, well, expect to start (if you play as rome on normal difficulty) with 141K right off the bat. I should mention that at this point, rome is not huge, it's not even all of italy yet. This makes armies more unwieldy, such that a tiny 1-province nation can easily throw a 20K stack at you and cause annoying damage.
2) AI won't surrender for anything. Expansion into existing nations is hard because even after you conquer them, unless you have 100% warscore, they'll be reluctant to accept anything.
3) The technology system is wierd. Even if you reach a certain technology level, there is only a chance that you will gain any benefit from it.
4) Navies are disregarded. If you remember your navy being your life line in EU3, well not anymore. You can easily go through the game after the first 50 years, with no navy what-so-ever
5) Omens. For an otherwise realistic game, incorporating magic is an odd choice.
6) Your generals can refuse, yes, they can out right refuse your holy god-like command from above to leave their army or even split it. (Imagine your whole army is in one giant super-stack of troops. Now imagine you get attacked from the south and north at the same time, but your general won't let go of the army to split it into 2. What now?.... your stuck paying upkeep for excess troops in the south, while barbarians run rampant and wreck stuff in the north. Ruins the game. Just shut the game down, delete your hours of progress, and go back to EU3)