This is one of my favorite films (with a Charlie Kaufman script). I love how it casts Jim Carrey and Kate Winslet against type (in terms of their extroversion/introversion factor) and both pull it off.
I get Joel better, he's much closer to my personality than Clem's ESFP style personality... but I'm more aware of his faults as well. Yes, Clem is the more overtly destructive, yet I understand why she gets frustrated with Joel. She wants directness in expression of needs, whereas Joel shies away from conflict and has trouble knowing or telling her what he wants. But the very thing that frustrates both of them is also why they are drawn to each other -- they both hate and admire each other.
I love the subplot between the doctor and Mary as well. It's heart-wrenching. And Patrick... wtf man, it's one of the few times I've seen Elijah Wood cast this way, lol, it's a nice unexpected thing.
There's also a counterpoint between them and Joel's friends -- the couple that seems to fight a fair amount, yet they stay together because, well, they have decided it's okay for them to argue and not get along sometimes.
This film always makes me cry. It's kind of a lesson on the perils of trying to avoid pain and grief in one's relationships, or having unreasonable expectations or thinking the best relationships have no conflict or suffering involved. The more that Joel is stripped clean, the more he digs down and can vocalize what he was actually thinking and feeling and what he wanted and maybe didn't get. The memories on the beach are so sad. But I love how "meet me in Montauk" lingers. Even in the grief, there is still hope something better can be built.