Since I am awfully down on Mantlo's run, I thought I'd point out some of the GOOD things that I have gotten from his run (or some of the better things, anyway):
*Northstar's Snark: Undoubtedly probably one of my most favorite parts of his run was Northstar's snark with Heather and others on the team. He had every right, usually, to be a snarky jerk, especially with all the "joking" and "teasing" that went on about his sexuality.
*Marrina and Namor: Namor is one of my favorite characters, so I love seeing him in other books whenever and wherever possible. Lately, I'm kind of used to seeing Namor written out of character (New Avengers, mostly), so Mantlo writing him somewhat out of character didn't bother me so much because at least he wasn't made to look like a complete jerk. However, Namor SHOULDN'T HAVE TO chase women (corrected for all you Sue Storm fans *HUGE SIGH*). And, honestly, while I found it kind of sweet that he was "willing" to take in Marrina and her pustule babies, that didn't quite sit right with me either. 1. Marrina is just as awesome in the ocean as Namor. She may not have his strength, but she can navigate around in the ocean and swim just as well. 2. Taking in Marrina and her pustule babies like she is a charity case of love? His kingdom was broken and he was the creepy lovesick one.<---this is how Namor was written out of character. Sure, Namor's kingdom is typically broken somehow as it brings him back to land where writers are more comfortable writing him (Roy Thomas was one of the only ones who ever could write him in Atlantis well), but chasing Marrina is nonsense. But the few books from that situation were actually funny to me. Lovesick Namor is hilarious.
*Goblyn: I LOVE GOBLYN. I agree with FP about her creation and things wrong with all of that, but I freaking love Goblyn anyway. LOVE HER.
I'm sure there are some other minor things that are positive that I have taken from Mantlo's run, but those are the major things for me.