I tried it from the first release, but I was disappointed because of the "heavyness" of the indexing process: all my apps seems to be like "yawning" at every interaction I did.
But because I like Google (yes, I said! I like it!) I thought "why don't give to it another chance?".
I'll let you know if all the improvement are enough to "avoid to kill the performance of my pretty honey [en:iBook|IceBook]".