I'm currently doing a research year between 3rd and 4th year, so I will try to offer some impressions about clinicals. I'm intending to match into a competitive surgical subspecialty, so what I say will probably be biased in that direction.
First of all, I think that when I was a premed and while I was interviewing, I paid a lot of attention to the preclinical curriculum because that was more like what I was used to in college, and I mostly regarded the clinical years as a black box that I didn't really pay much attention to. When I became a 3rd year, I realized that it's actually all about the clinicals. How you do and what you do in your clinical years (3rd year in particular) will really mean a world of difference for how you choose your career trajectory. Clinicals at important, so ask about them!
Without getting too much into the specifics of the clinical schedule, WashU offers quite a bit of opportunity for 3rd-year exposure to subspecialties and smaller specialties. For example, you have the option to do an in-patient Cardiology rotation while on Medicine, the option to try out basically any surgical subspecialty you want on Surgery (including ENT, Plastics, Urology, Optho and many different areas of Ortho), and an elective month that you can fill up with everything from Path to Rads to Derm. When I entered medical school, I really didn't have a great idea of what I wanted to do, so it was great for me to be able to try all of these different things without having to wait until 4th year (at which point, you will have less time to decide and prepare for your specialty of choice). In the same vein, there are no required 4th year rotations, so all of 4th year is essentially your opportunity to fill in any gaps that you might have and to strengthen your residency application however you see fit.
I'm told that we have one of the most benign Gen Surg residency programs in the country, and I can attest to the fact that during my entire time as a 3rd year, I've only met maybe 1 person that I would consider "malignant." The vast majority of residents, fellows, and attendings are all very nice and willing to teach. 3rd year is hard work, and you will be taking overnight call on several rotations. Our most hated rotation is probably Neuro, victim to particularly harsh coursemaster, large team sizes, and an extremely busy service. Our Peds rotation is also felt to be harder than most others. On the other hand, our Medicine rotation is universally well-loved.
I'm not sure what else to say at the moment, but I'd be happy to answer any questions.