I shoot RAW and tend only to put in the minimum sharpening needed, often leaving Photoshop,or Lightrooms default settings as standard.
As you are applying unsharp mask I assume you have Photoshop. Now if you have CS3 there is a great module built in. It's similar ( almost identical) to the develop module in Lightroom. And you don't have to shoot RAW to use it.
The nice part is the sharpening controls. OK so how do you set it up for jpegs.
Go to EDIT> Preferences> FILE HANDLING. and tick "prefer jpegs in Adobe Camera RAW.
This will open jpegs in the RAW workflow window. Lots of great controls and some a lot easier than the Photoshop ones. Now back to sharpening.
In this module select the sharpenning window. It's the 3rd one along with two triangles. OK now zoom into 100% . It only works at this magnification. If you now hold down the alt key and adjust the slider's, the image will go monochrome and you'll be able to see the effect you are having as you adjust each of the controls. Why monochrome? because the module is only applying the sharpening to the luminosity channel not the colour ones. Thereby reducing "noise". This way you can easily appreciate the changes you are making. Release the ALT key and it reverts to normal colour.
When you've done click on the "open Image" button , bottom left and you're back into Photoshop as you know it.