One should not view Subject Two expecting a work of epic proportions and impact, as the film wishes to be at its core. Because it would only disappoint and maybe it just isn't worth any disappointments.
The story, well knit together, involves a failing medicine student and a mysterious doctor Frankenstein figure who try to redefine life and death. While this may not be such an impressively original concept, the film still works as a whole out of two solid reasons: up to the task acting and some thought-inducing (if not, once more, thoroughly innovative) ideas.
Given that the basics are there, 'Subject Two' is what I'd call a film with limited potential. I do not believe this theme can be exploited any better than it has been in the past and it'd have to show off something utterly brilliant to sweep me off my feet. A very gentle 6,5 from me.