In this site’s about section we discuss why to use a reverse macro lens, so I thought it would be important to get some comparison shots with real macro lens at a close to the same magnification.
Here is a sample of the difference on a Canon Xt shooting a Canon 100mm Macro vs a Reversed [...]

I took this the other day in a garden of a friend of mine. They were shot a reversed 18-50mm sigma lens and a Canon T1i body. I am fairly happy how the $70 lens turned out as a macro lens.
Rose Pedals:

Bee Collecting Pollen:

Rose Bud:

User MawcDrums on youtube uploaded a quick how to video about how to open/close the aperture when you are taking photos when you reverse a camera lens for macro photography.

The results are a bit iffy to see on the screen, but you get the idea.
It was taken on a Canon Xsi with the kit lens.