I was one of the people who liked Secret Wars at first (# 1-8) then hated the rest, where Dr. Doom gets the Beyonder's power.  I thought Shooter was just losing it at that point.  Secret Wars II was even worse.

But I do think some crossover events have been handled reasonably well: Secret Invasion and Dark Reign in particular (just started reading the latter finally but have enjoyed it so far); World War Hulk (though I'm still trying to figure out when that event "happened", vis a vis the New Avengers).  Didn't particularly like Civil War but that may partly be because of Millar.  Hoping "Siege" holds up; haven't gotten to it yet.

I'm also thinking of picking up the Acts of Vengeance omnibus, although I haven't heard much about that storyline one way or the other.