As I don't live in NYC, I usually hear the music before I see the show. If I tried to see every show before I bought/listened to the CD, I'd never get to listen to anything.
I bought
The Light in the Piazza right after the Tony's last year, becuase I was blown away by Kelli O'Hara's voice (and I usually don't like sopranos). I saw the show later that summer, and was very glad that I already knew the music. I was able to spend less energy focusing on understanding the story/lyrics, and more energy noticing the nuances of the performances and the relationships between the characters.
I am a little concerned about seeing
Q this summer, for the same reason as mentioned above. I already know all the funny bits of the songs, and have seen the show thanks to some nice *footwear*, so I'm worried I'll end up disappointed.
On the road of life, do not pause for suicidal chipmunks who freeze in your headlights, seeking death by your tires...