The BA First Lounge is perfectly OK, nothing special, and from the outside the Aer Lingus Gold Circle lounge at BOS looks fairly similar in terms of offering but more recently updated and with more natural light. It's also near their usual departure gate so I think the Original Poster will be well served by that, that's certainly where I would go.

I'm a Lufty Senator and I have to say that if anyone thinks that Star Alliance offers a better lounge provision than oneworld they are clearly flying to different places than me.