I don't know which Olympus model you're thinking of but I can speak from my experience with the C-7070. The supermacro mode is certainly not a gimmick and it works very well. In regular macro mode you can still use the zoom and flash but in super macro both of these are unavailable and the lens moves to a fixed "medium" focal length. While in super macro mode you can actually focus from 20 mm (approx) all the way to infinity.
No sure exactly what your questions means but SM mode isachieved mechanically and utilizes the full sensor size, so it's not just electronic / software processing that (for example) uses just a centre portion of the sensor (like "digital zoom").
I don't have my best SM examples to hand but the attached will serve as an example (taken in SM mode with ISO 400, 1/320 second at F4.5). Examples taken in better light at ISO 80 or 100 are much more impressive.
I hope this is helpful.