You should be able to use the miles on SAS however, it depends on USAir’s program.  You should call their mileage reward booking and ask them for specific SAS flights.  If there was reward seat available on the flight, it should be no problem.
 
I have flown SAS (although only within Europe).  I wasn’t impress.  If I were you I would save the points for flights on Singapore Airlines.
 
 

i’ll be flying from the east coast of the US into europe. should i just stick with usair, or is there a better star alliance carrier that’ll provide more comfort?

I agree with apyf, SAS really isn’t anything to write home about.

Lufthansa is respectable – nothing amazing, but always good service & usually on-time & professional.

Some of the smaller STAR carriers are actually very nice, like LOT Polish – great food service and nice feeling on the plane. United and US are not the best for Intl’ travel.

Forant, if you only have enough points for economy class I don’t think there is must difference in the level of service between the Star Alliance airlines that offer direct East Coast US->Europe flights.  If you have points for Business or First class, the European carriers might be a better option.
 
Check out http://www.seatguru.com and see what the different airlines/planes offers in terms of entertainment and seat pitches.   Else I would just select whatever flight they have award tickets on (international award tickets aren’t the easiest things to get now a days), and would get me to the destination quickest with minimal stopovers.
 
Check this for airline reviews: http://www.airlinequ…
 

SAS are good transatlantic; o.k. intra-Europe, but nothing to write home about. I would not hesitate to fly with them again (and in fact I will next month).