What a polarizing headphone! I can see where you guys are coming from. I spent more than a year debating whether I should get it (since I didn’t have a chance to demo it) since opinions were so contradicting. In the end, I figured why not. Blind purchase it was!
For me I personally adore the MDR-Z1R’s fun and musical sound signature (I say that as a long-time owner of the IER-Z1R). True - the MDR doesn’t slam as hard or screams as much as its in-ear brother (cousin?), but it’s super comfortable for a long listening session.
I haven’t tried with a computer yet - I only ever plug them to my Walkman and I think it has a built-in amp chip. The sound I get from that is reasonably loud (the volume knob is 3/4 of the way). I also EQ the shit out of it to get the sound I want.
From what I’ve heard the MDR-Z1R isn’t that hard to drive so you might get something out of your MBP. That said, whether the combo produces good synergy is another question for you to find out.