You're gonna get a lot of varied answers, but I personally loved it. It was unlike any other theater experience I've ever had, and the cost of occasionally seeing backs to me was worth it to have the actors sitting next to me and to be so close to the experience that is happening on stage.
I'm gathering that where you sit on stage might matter, not in terms of which side of the stage you are on but more how far away from the orchestra you are. I was as far away from the orchestra I can be, aisle seat near the audience, and I didn't feel like the music was too loud or that I missed lyrics, but I think people who sit closer to the orchestra complain more of that aspect.
"If there was a Mount Rushmore for Broadway scores, "West Side Story" would be front and center. It snaps, it crackles it pops! It surges with a roar, its energy and sheer life undiminished by the years" - NYPost reviewer Elisabeth Vincentelli