Is there a way to improve the appearance of a covered front porch roof that uses corrugated plastic roof panels?
One of my business partners is a roofing and gutter company in Eastern NC.  It varies, but code requires a membrane roof on a .25/12 pitch and I have seen a number of houses around here with a small covered entry like what you describe with a EPDM (black rubber membrane) roof.  Typically it will be trimmed with a metal edge band and doesn't look bad at all.  

My concern, at least around here, would be when we get a good rain with wind involved.  The water may not drain off fast enough and if the wind pushes it against the house, you have potential for water to find it's way in.  Therefore, I would recommend flashing the membrane up behind the siding or fascia depending on how you frame the roof.

EPDM (rubber membrane) roofs this small are within the realm of possibilities for a do it yourselfer.  Be sure to do your homework on how to install these and take your time to get any and all wrinkles out of it.