Starting my 2nd year of med school.
1. What I liked about the transition? Working during the day and sleeping at night! Always getting off on time (so to speak). But, seriously. It's exciting to be moving on to a new extension of my career, learning new things, and getting a deeper understanding of stuff I've done and seen on the truck.
2. How long? 13 years in EMS- Started as a dispatcher and non-certified driver, worked all the way up to Paramedic supervisor.
3. my EMS experience was a double-edged sword. Some places it helped immensely, like our Doctoring Skills course, where we learned how to take BP's and listen to lung sounds. but it hurt me some in cardiac physiology-I fell back on what I had been doing for years to read EKG's and got test questions wrong. I have to make myself study certain subjects more (i.e., like this years Pharmacology), so I don't fall back on experience or assume I know it already because "I studied it in medic school and have used it for years".
I agree with what alpinism said above. If your ultimate goal is to become a physician, Working as an EMT while in undergrad is OK. Paramedic school is a pretty intense academic endeavor itself. I was already a medic when I started undergrad, it was difficult to keep up with schoolwork, MCAT prep, supervisor responsibilities, etc. It did play into the strength of one of my recommendation letters. As far as working while in undergrad, I started on the truck-working straight nights on the 2-2-3 schedule, then transferred to straight days in communications and went to evening classes, then found a service where I could work a straight 48 on Saturday/Sunday and go to class full time (sucked, but it got me through Organic Chem). That lasted a year before the paychecks started bouncing and accusations of Medicare fraud and bankruptcy ensued. Finally, I pieced together 3 part-time jobs to be able to pay the bills and finish school. Be careful piecing everything together, make sure when you schedule your pre-req courses, you don't overload yourself and can keep your GPA high. I made that mistake and triple-stacked Physics, Biology and MCAT prep while working and didn't do as good as I should have in any of them. Good Luck, It pays off in the end! PM me if you have any questions.