Pianos are OK in the right place - but thats not in most folk music scenarios.
I have found that piano players are in the most part very unweildy and not willing to alter anything to enable other instruments to join in. EG its difficult to play some pieces in certain keys on guitar/banjo/recorder etc and where we would be happy to change key to accomodate, we have never yet found a piano player who would.
Played as a sol instrument thats fine - but otherwise NO