I only sharpen for the final Output none whatsoever in Camera nor RAW conversion.
As you know, there are many who see sharpening in three steps:
Capture - to restore "natural" sharpening lost by the analog to digital conversions and high pass filters
Creative - to emphasis some photo aspects, commonly the eyes in a portrait
Output - based on final image size, image resolution, and output media
I agree with David, Aperture's edge sharpening brick is very capable. Its kind of like Lightroom's sharpening, but with the edge mask already built in. I can get done what I want to get done with it.
But output (really only for print) sharpening in Aperture seems too basic with just amount and radius sliders. And there is no creative sharpening beyond a round trip to Photoshop or a sharpening plug-in.
If I were to follow Jeff Schewe's advice about print sharpening, and wanted to get a sharpening halo of between 1/100" and 1/50" I should be able to select a sharpen radius setting with knowledge of the output resolution. For example, if I'm printing a file at 792 dpi (I know Aperture and/or the printer driver will downsize that to 360 dpi for my Epson R1900), I'd need a radius of about 8 to get a sharpening halo of 1/100", true? But 8 sounds like a big number, maybe only because the image resolution is so high.
I know the sharpen amount is in relation to my output media, but how do I figure the setting for matte, or glossy paper?