We started playing music in our infant's nursery after our first visit to his daycare, where we noticed them playing music in the crib room to provide white noise for the sleeping babies. The idea of a lullaby-ized version of music we already enjoy listening to appealed to us, so we started out with this CD along with a couple of other titles. We've enjoyed the series so much that we're now up to ~15 of these, if for no other reason than to provide US with some variety as we rock our child before putting him down for the night. By removing the words and playing the songs at a more or less constant volume, they provide a soothing bedtime experience without the sudden changes in volume and tempo that might otherwise startle or excite a child that you're trying to get (and then keep) asleep.
As a general rule, they've all been fairly enjoyable, but my wife and I both agree that the Coldplay CD is clearly a cut above the rest. Given that neither of us own or regularly listen to the real Coldplay albums, and that there are several CDs by some of my favorite artists in the Rockabye baby collection, this is saying quite a bit. For whatever reason, when nothing else will soothe our child, this particular album ALWAYS works. If you enjoy Coldplay, or want to give the rockabye baby series a try, this is definitely the one to start with!
I would also highly recommend the Rockabye Baby Guns N' Roses, Led Zeppelin, Queen, Rolling Stones, More Beatles (the first one is not as good), and Beach Boys albums.