I love Sondheim shows, but there are a few moments that bore me.
For example, there are parts of ITW that bore me, mostly the dialogue, also a few songs such as It Takes Two, and parts of So Happy.
Though it is my favorite show, No Place like London in Sweeney Todd always somewhat bores me, especially after the thrilling Ballad of Sweeney Todd.
The bginning of the Ballad of guiteau and most of the Gun Song in Assassins bore me.
However, most of the Sondheim shows I like keep me entertained and attentive. These moments I mentioned are boring, but the interesting and entertaining moments in his shows far outweight the boring moments.
I am a firm believer in serendipity- all the random pieces coming together in one wonderful moment, when suddenly you see what their purpose was all along.