Dalton is always super fast to respond to emails. I've gone back and forth with him, asking lots of questions, and really drilling down to make sure I understand what he is suggesting. Without fail, he'll get back to me within a matter of hours and respond in-depth to my questions. I think his background in psychology and experience working with younger populations gives him very insightful perspectives. He is also very honest and supportive.
Alexis is one of the people I most admire. The guy has real integrity. I think he understands what is truly important in life and lives in a manner that holds up these values. They are implicit in how he relates to others. He is also an amazing worker. I remember asking him for a consult on a Saturday morning. I was thinking we'd connect later on that next week. He got right back to me and called me on a Saturday morning. I apologized for bugging him and he said not to worry that if I'm working he is working. Then, to take things a step further, he connected me with Ashley Dawkins (his Outreach Director). She is also awesome, quick to respond, and very helpful. The last point I'll highlight is Alexis is really hopeful. Hope is pretty damn powerful and I think he gets that in manner that few people understand.
To wit: 2 years ago Kat was my right-hand and now she's a partner + runs outreach at YC.
In particular, Dalton is someone that helped us when we got rejected after our first interview, stayed supportive, and always has actionable insight and advice. He's also just a legend.
As to Alexis, I honestly don't understand how he does all the things he does - he's just going at like a million miles a minute. As high profile as he is, I actually think his value is underrated in the YC community.