I attended UW both as an undergraduate and now for med school; I am a nontrad student, and at least a part of my nontraditional status is due to exactly what your complaints are regarding the undergraduate portion of the institution. It is huge, very impersonal, your profs don't know you, don't seem to care to, and advising is substandard.
That being said, I can honestly say the med school is completely the opposite. Think of a small town high school where everybody knows everyone else. Professors tend to have office hours everyday they lecture right at HSLC- and the majority are genuinely interested in seeing you succeed. There are TA's for every course, who can also be helpful. There are two learning specialists (?I think that is their title?) who are there to help with suggestions and set you up with a free tutor if you want one. My understanding is that if someone does not do well, people will "come out of the woodwork" to help.
Are there occasional lecturers who are not invested in our success? Yes- but the course directors and TA's are available. I did a second undergrad at a smaller institution within WI prior to med school, and the atmosphere here at UWSMPH is more like the small institution.
Feel free to PM me with any questions- we have block exams next week, so it may take me a week to get back to you. I would also encourage you to take a second look at UWSMPH and ask all of the questions you have of current students. Good luck with your decision- and Congratulations!