If you've played the first No More Heroes, you pretty much know what to expect.
There are more assassins to fight here, but the game's length is about the same as the first. The overworld has been removed, which is good considering that it was somewhat bland in the first game. You also no longer pay to fight for the UAA. Instead, money is used for clothes and new beam katanas. The job system from the first game is back, but most are now played with an 8-bit system, a throwback to old-school video games. There are also two characters that become playable mid-game: Shinobu and Henry. Shinobu is used for two whole rounds. Unfortunately, Henry is only playable during one fight (although it happens to be my favorite battle in the game).
Now for the negatives. The camera troubles from the first game have not been taken care of. In fact, they are worse. Slashing a bad guy near a corner causes the camera to zoom up really close to Travis. While the story starts out pretty good, the ending (particularly the battle against Batt) could have been better. The constant battling on the supermarket parking lot level also got REALLY repetitive. It's like I was pushing buttons and waving the Wii remote constantly for 10 minutes non-stop. Not fun.
If you liked the humor in the first game, there is more of it to be had here, if you can get around the faults.