Anyone can have an understanding of how research works by reading up on it. "What is this thing called science?" by AF Chalmers gives a very good understanding about how science works. However, in most cases (and I mean 99.9%), an intimate understanding of research in practice is not achieved at the undergraduate level even when you've worked in the lab for 1 year.
I'm sorry but I'm not convinced research is useful to any medical student unless he/she intends to engage in some form of research. There are successful MDs without an iota of research experience, thus demonstrating that prior research experience is not necessary to be a good doctor. It's also not necessarily true that research enhances "background reading".
Depends on what you mean by the bolded statement. If you're talking about project design, data interpretation, performing day-to-day experiments, learning to interact with a PI, and gaining experience making presentations and writing scientific literature, I'd say your statement is absolutely false. These things are achieved thousands of times over by premed students; I know because I've interviewed them and got to do this sort of thing myself as an undergraduate.
IMO the biggest reason research as an undergrad is useful as a medical student is the practice with presentations. I know I was terrified the first time I gave a scientific presentation at a conference as an undergrad, but after a few it gets a lot easier. I have no problem speaking in front of 100+ people, and the only reason is because I've had practice doing it. This skill alone has been useful many times over the past few years. The other thing this ties into is presentations to residents/attendings. You'll be doing this multiple times a day as a third/fourth year student, and if you are a confident public speaker it'll help a lot. Sure, you could probably get this experience through a public speaking class or something, but why not get the experience and throw some posters/publications on your CV?
Another issue to think about here is that at least in my class, the majority of students end up doing some type of research at some point. Want to do ENT, radonc, plastics, derm? You will do research, and may even take a year off to do it. Want to do neurosurg, rads, ortho, urology, anything with a 240+ board score average? Probably should plan on some research at some point just to keep up with everybody else (check out charting outcomes in the match and look at "mean # research experiences" for matched applicants). Any training in undergrad you did in research will help you here.
The two sentences in your second bolded statement are not related. I wholeheartedly agree that successful physicians do not need research training. However, this fact has nothing to do with the sentence preceding it. IMO doing research as an undergrad/med student is useful for a number of reasons that I've mentioned. Maybe the most important reason, though, is to get into some of the more competitive specialtys, some of which have a pseudo-requirement for research depending on the chair at your particular program.
