In terms of getting experience with the cerebral and day-to-day work flow aspects of medicine, scribing is pretty much second to none. You get to see how patient encounters work, how patient disposition is decided, and the elements of medical decision making. It's a great experience for understanding what doctoring actually is on a day-to-day basis over a long period of time that most people don't get just with shadowing.
What you don't get much of is actual direct patient contact (at least where I work), so I found it pretty important to supplement it with opportunities where you are actually directly interacting with patients.
I have loved being a scribe so far (as my name probably implies), and it was probably the most important experience for me for figuring out why I wanted to be a physician. I love the culture where I work and have had the opportunity to see and learn some incredible things. From what I have read from other people around here, this might be partly due to the group I work for (we are directly employed by the emergency medicine practice group that staffs the hospitals we work at, and they put a ton of effort into making us part of the department and mentoring us), but I don't think the core benefits of the experience change much based on location.
As far as your specific questions go, full time versus part time and the length of your commitment will depend on where you work. At the group I work for, scheduling is usually extremely easy because it is all shift work. As long as the shifts are covered no one really cares how much you work unless you want benefits. Scribes are usually young and don't have major external commitments, so shift swapping is pretty easy in the event of any conflicts or even if you just want to move between part time and full time in terms of hours. This is pretty much what I do right now because I work two per diem jobs and my schedule is extremely variable.
They technically expect a 2 year commitment for part time but 1 year for full time where I work, but they obviously can't force us to stay. Usually the leverage they have for this is denying any letter of recommendation requests if you break the commitment.
Pay is variable, but generally not very high. I make enough to live away from home (but with roommates), and that will probably be true for you if you live in a low cost of living area.