I don’t know if my experience is considered typical. I worked as a TA in the algorithms course and then in Computational Photography while I was there. The algorithms professor was actually how I found the SV job I moved here for. I’ve seen it mentioned elsewhere already, but I can confirm that TAs run most classes—but it’s also worth pointing out that TAs in OMSCS are often comically overqualified, and 90% of the work in running a course is logistics (due dates, extensions, grading, etc.).
I think it’s as valuable as a resident program if you can’t justify leaving your current job or taking on debt to finance an advanced degree. Just make sure you try to learn everything you can while you’re in it.