Pretty much the same experience as inFamous with only a few slight changes.
The ending makes thinks much more interesting but getting to that part can feel like a chore at times. Missions tend to be varied, but most of the times, especially side missions, are all about defeating lots of enemies. Completing side missions sure pays off though, as you are rewarded by some excellent power ups like draining electricity at a faster rate, and an ability to sense collectible upgrades at unlimited distances, making those damn blast shards a much less tedious part of the game than it was in inFamous.
There are plenty of bigger and tougher enemies this time around, but they make a habit of appearing too often thus making it a chore to deal with them over and over again. New melee attacks are fancy with plenty of camera zoom-ins making close combat fun to engage in. The are many abilities and powers to chose from this time, you can make your own set of preferred powers as you unlock new ones by a simple quick select options in the heat of battle.
Many of the characters are simply shallow and unlikable, and instead of fleshing them out the story seems to be concentrating on aspects you won't be caring about.
The good and evil system is completely black and white, but many missions are divided by that system so that might make you decided which path to take and will probably result in an interesting replay.
The town is filled with random karma opportunities such as robberies or bomb defuses, giving you an unlimited supply of karmic choices throughout your travels. The user generated content gives you an unlimited supply of missions to play, but won't reward you with the combat experience gained by farming them. The mission maker is very complicated so you will be turned off to make great missions sooner than you think, also many people are using it just to fool around so finding a really good mission can be a hassle. Thankfully by using the filter system you can probably find what you're looking for.
If you enjoyed the first inFamous, you will certainly find fun with inFamous 2, just don't expect ground shattering improvements like those of Uncharted 2 or Assassin's Creed 2.