I read this for Banned Books Week 2013.
What I enjoy about this play is the seemingly haphazard appropriation of lines from multiple Shakespeare plays, which I always find an interesting technique. Though it doesn't seem like Garson is particularly concerned with appropriating lines in any systematic or purposeful way--for instance, while there are sections that seem to link Bobby with Hamlet (another famous, if problematic, revenger), but then MacBird also gets some of Hamlet's lines.
In terms of the play's purpose, it feels really narrow and severely dated. I mean, my sense is that few people today hate LBJ as vehemently as Garson seems to, and although JFK is still a kind of culture hero, we also know that he wasn't as much of an angel as he might have seemed at the time. Partially I think my dislike for this play is because I feel like LBJ got unfairly blamed for the Vietnam conflict, when really Kennedy had begun US involvement, and I do think LBJ's Great Society program would have been good for the country if not for the war destroying his credibility. Basically, I feel this play is really unfair to LBJ.
However, I did actually like the end of the play when Bobby seems to turn. He gives a fairly absurd explanation that Joe Kennedy had had his sons' hearts and blood removed and replaced with machinery to make them better leaders--suggesting that Bobby Kennedy, for as much as he's the hero of the play, will perhaps not be a substantively different leader than MacBird. This impression is bolstered when, in the last two lines of the play he pledges his solemn word "to lift aloft the banner of MacBird" (III.vi). I'm not sure what we're supposed to make of this ending, but my cynical 2013 position suggests that Bobby is no longer the hero of the play, but is poised to become another tyrannical leader in the vein of MacBird.