Mostly, I liked NMH2, and if you liked the first one you'll enjoy it to an extent, if for nothing else because it's more of the same. The main problem with No More Heroes 2 was that the bosses just weren't as memorable or interesting. Both games are very focused on the boss fights: the minigames are maybe fun once each, the levels before the bosses aren't terribly interesting (and yes, they do seem to get overly long toward the end of NMH2), and the assassination missions are just shorter versions of the levels before the bosses.
But unlike NMH1, the bosses in NMH2 don't seem as strong from a character perspective: you kill them in an attempt or two, then instantly forget them. Margaret seems like an attempt to recreate the success of Bad Girl (complete with "catchy" theme music), but Margaret doesn't have nearly the WTF value: she's just some random assassin with obnoxious ranged attacks. The game tries to make this into ironic commentary on Travis's bloodlust (the rank 2 boss even telegraphs it by asking if you remember any of the people you've killed, and you generally don't know the assassins' names until afterward, unlike NMH1 where they're introduced at the level select), but "ironic commentary" doesn't make it a more fulfilling game. And most of the hard ones can be cheesed by taking the Peony (a long red sword that gets longer, harder, and redder the more of a combo you build up... can you see the obvious joke being made here?) and bludgeoning the enemy to death with it without much real strategy.
Nowhere is this more clear than in the last boss of each game. The last boss of NMH1 appears once, he killsteals you (although apparently not very well, given one of the bosses in NMH2), he jaws with Travis for a bit, then the fight gets broken up. Okay, now we have a rival, who's kind of like Travis but more of a jerk. So when he shows up at the end of the game, it feels satisfying to duel him, and if that's not enough, there's the "plot twist" to make you realize that he's actually a semi-important random jerk. And the fight is reasonably satisfying: no real tricks, but sometimes you don't need tricks (see: the last part of the Ganondorf fight in Twilight Princess, a similar situation).
The last boss of NMH2 seems like he should be important: he's the reason your friend died, he's the CEO of a large and uncaring corporation, and he's a callback to the first game (although for some reason his last name and his company's name changed?). The problem is that Suda 51 fails to make you actually care at all. Who cares, when Travis indiscriminately murders people all the time and the friend in question was even more of a loser than Travis himself? And the fight itself is just irritating: the first phase features a moment where with no warning your previous strategy just stops doing damage with no feedback from the game that you're not doing any damage, the second phase somehow confuses "difficulty" with "cheapness" by giving him an attack which is nearly unblockable and making you just wait for an attempt where he doesn't constantly spam it, and when you kill him there's no twist or resolution, just "well, now I've avenged my dead friend, time to not really resolve anything, THE END".