METCO Motorsports, LPE and I think KDi has an isolator also.
We've been installing the solid coupler/isolators for years now on the Eaton blowers. It is not just noise that you will experience when the isolator starts going, but you will see it show severe signs of wear. I have seen bad isolators on 1500 mile cars (as well as shaft wear), as I have seen them on higher mileage cars, and vice versa I've seen plenty of good ones still that we have changed because it is a must.
Here are some pictures of the wear on the shaft
Shaft wear 1,
Shaft wear 2.
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Here is a media drawing released from GM in late 2012 that actually identifies a solid coupler being used in the LSA motors.. Unfortunately that has not happened yet. There were talks that the new supercharger kit part number 19301022 includes a solid isolator. I can neither verify nor deny that, so take that with a grain of internet salt rumors!
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The very popular Eaton M62, M90, models that GM has used on various vehicles with the 3800 series motor (Grand Prix, etc.), 2.0L Ecotec Cobalt (M62 Eaton), does not have a torsional spring loaded coupler, as they have a solid one piece coupler.
Below is a picture of the Eaton solid coupler used in GM applications in the past.