I think MA's strength for oneworld will be in the European market more than the North American -- they offer some pretty decent opportunities for flights within Europe (especially to Eastern Europe).
That said, right now MA has some fantastically inexpensive flexible business fares ex-JFK right now -- often $2,200 with no advance purchase and no minimum stay. If they'd just let you add on an AA leg in North America for a little more...I'd like them a lot
Steve