Re: Preclinical curriculum
I'm a fan of P/F first year and then H/HP/P/F for second year. This gets revisited every 5-10 years, and most recently (~7 years ago, IIRC) the students voted to keep it this way. It helps those students going into ultra-competitive specialties differentiate themselves, and also the MSTPs that often have fewer rotation grades on their transcript when residency apps are submitted. As you can imagine, qualitative comments are often generic-sounding, so grades 2nd and 3rd year can give programs a sense of your relative strength. That said, the "middle 3rd" still does quite well matching. Also, I tend to be more studious when a grade is on the line, so having grades helped me get more out of the two years that form the core of your education. (That's why Yale's P/F all 4 years just wasn't going to do it for me.)
The P/F system first year is a nice way for students of varying backgrounds to find their footing and help each other out, killing off any latent gunnerism (i.e., maliciousness) that might have otherwise existed. P/F also allows for a very robust selectives system, where you take at least 4 short courses that fall outside of the core curriculum. Some of my favorites include Laughter and Medicine (in the process we learned some clowning and rounded with the Clown Docs in the hospital), Art and Medicine (held at various museums in St. Louis including a personal tour of a museum's print collection), Medical Economics, Health Policy, Public Health (I think through this one we did rotations during first year at the student-led neighborhood clinic), WUMP (week-long program just prior to orientation -- highly recommended), and History of Medicine (was a little dry, but we did get to walk away with a couple of old books at the end).
And outside of electives, people stay active through a myriad of clubs and groups representing any interest you may have, from writing and drawing to juggling and musical theater (did I mention we have student-run musical every year?) to lively community engagement. Coffee house hours are always amazing, too, when fellow students offer up live performances (rock, R&B, classical, spoken word, etc.).
From my experiences chatting with other students, both the selectives and the extracurriculars are more vibrant than anything analogous at other schools. Part of that is the nature of the students attracted to coming to WashU, and part of that is how the system facilitates and strongly supports students' interests.
There are also schools that trend towards having a test every week or every other week -- that would've been tough on me and any outside interests I have, since my friends seemed to always be studying for the next test, and falling behind on everything else.
Downsides to 1st two years: a few blocks tended to have more class time than felt necessary, technology is being utilized in some helpful ways (lectures are now videotaped, online self-assessments and study tools, there's an iTouch pilot program going on for clinical use rather than PDAs, etc) but we're not at the bleeding edge of technology adoption. Less time than most places to study for Step 1 (~4 weeks most years), but overall we still do quite well. I'm sure there were more grievances, but it's starting to feel like a long ways back into the past.
Of note, the FLTC is very nice and very functional, something that's hard to appreciate until you actually find yourself studying or working there.
One last thought: a common complaint is that we don't get free printing from the computers in the carrels. If your biggest complaint centers on 5-cents-per-page printing, then a lot of things are being done right. (Remember, you can always print double-sided, and often multiple pages per side. And if many students want a lot printed [like slides], the administration will take care of it... for free.)
Dr. Koong-Nah Chung and Dr. Will Ross
She interviewed me, and she's as nice as can be. We ended up spending most of the time talking about our families. And Dr. Ross is an inspiration and has done a lot for the city, though he's very humble about his contributions. Just relax and have an easy chat with both of them.
Inter-class cohesion
This by-and-large depends on how involved individuals are. Some people definitely mix more than others; it's really hard to say anything in comparison with how it is at other schools.