I am (still) a medical student at Johns Hopkins, and I love the place very much. I have for the past 6+ years.
After my third year, essentially on a whim (my sponsor, I think, knows this) I pursued a research fellowship in cardiovascular genetics. I loved it a lot, and stayed on a second year (spontaneously; thank you, Stanley and Lola J. Sarnoff).
After my fifth year in medical school, my second year of CV genetics up at MGH and the Broad Institute, I got the opportunity to pursue the startup dream for a year. I'm midway through and absolutely loving it.
But yet, I miss medicine. And I think that the grass is always greener, so I think I will miss whatever I'm not doing. Next year, in medical school for the first time in three years, I will miss research. Or I will miss the startup life. Something. I know it, because right now, I miss the hospital.
I miss working 80 hours a week while paying $50,000 a year for the privilege. I miss having a best answer (and if you think there are better answers in software than there are in medicine, please email me so I can hire you).
But I know that soon, I will miss the freedom of working at a startup. There is no right answer for everyone. And for many of us who were drawn to medicine, I think there can be no possible right answer, ever.