Yes, you have to hide a lot of complexity and only focus on one problem/asperct per week, but it is doable to teach pure 3.2 core in an introductory CG course. The feedback was good and it's even more obvious to the students why we teach the basics and the math behind graphics: you have to implement it on your own in the shaders (these is no magic gluLookAt and glVertex() so you don't need to understand the modelview etc.).
On a personal note, I'm strongly against teaching the immediate mode in 2012 as providing one vertex at a time (and a predefined set of vertex attributes) is not how the GPU works and it's not how graphics work anymore. If I would teach my students outdated stuff with no relevance to the real world that does not even support them in understanding relevant basics, I would fail as a teacher IMHO.
* there is no reason to stick to the immediate mode for teaching
* teaching core and shaders from the beginning works
* udate your curriculum