Hey,
The Pros are: 1. Only one class to worry about, so there was plenty of socializing/ night life type things (other than the few days immediately prior to an exam). 2. I felt the small anatomy lab was helpful for me to get the professors attention and made it possible for the whole group of us (between 30-40 usually) to socialize. By the end, we all knew each other very well because there were only 40 and we spent all day in lecture and lab together. 3. The free time during the first 4 units (from August-November) while the rest of the class takes anatomy was awesome. Personally, I shadowed every week in three different specialties. Some set up research in the spare time and others just took it easy. 4. The best part for me was the fact that I got to focus my studying time on the Biochem/genetics course. I hadn't taken these in 2 years, so I appreciated the extra time to spend on re-learning the wonderful world of biochem.
The Cons: 1. When the rest of the class comes, you tend to continue to hang out with the summer anatomy group simply because you know them well and know what you have in common. That said, we are all grown adults, no one was 'outcast' because they were in summer anatomy. When we made the effort to meet everyone from our class, there was no problem at all. 2. You do lose a large chunk of your summer. There are three weeks between anatomy ending and the orientation, during which I went on vacation and many others did as well. If you are coming straight from undergrad, you might feel differently about losing your summer.
I took time off between undergrad and med school, so I felt summer anatomy was a great way to get back into the swing of things. Given the chance, I would undoubtedly do it again, just for the extra time when the rest of the classes start and the smaller anatomy lab group.
Also, remember- medical school is not a death sentence. You will continue to have a life and have time to yourself. If you don't have outside interests and choose to spend 100% of your time on medicine, you aren't benefiting yourself or your future patients. Taking care of yourself is just as important as taking care of your patients.
Hope this helps a little. Let me know if you're curious about anything else re Upstate.