I think it depends on what you're trying to render. If you're using any lighting using Uberlighting and transmapped hair, the render times will go up. However, there's a trick using the included ubersurface (I forget where it is since I'm still jetlagged after spending 3 weeks in europe and I use a related product Uberhair... someone can point where it is)... but you apply that to the hair and turn off the raytracing and shadows and that will reduce the rendering time. 

But you apply it by going to the surface tab and selecting the hair, then hold down the ctrl and double click the ubersurface icon. That will give you a dialog box and you change the bottom drop down to "ignore". This will copy the ubersurface settings to the hair without wiping out the current textures. Then back on the surface tab, find the new settings in the hair for raytracing and shadows and turn them off.

Then render.