In LR3 on the G1 I use 45,1,40,0 from the sharpening for low ISO. Noise is luminance 12 with other settings default. Medium ISO I increase the sharpening by around 10% and the luminance to at least 20. In any image where the noise is genuinely visible, I will set luminance and sharpness to zero and process with Topaz 5, bring up the sharpness again later on the TIF. It's important to keep the colour noise reduction in Lightroom at or above the default as I don't know of any other software that can match this excellent performance.
Small adjustments make no visible difference but I do find that having both sharpness and luminance well above the default make a good combination
Oh, and I usually boost the vibrance as well a bit though I doubt it's necessary with a lens like the 20mm