Google has recently released the collection classes and associated utilities that they make use of internally.  These are an extension (and improvement) on the Java Collections API.

I personally find that the Java collections API serves me well.  I have slowly started to switch a few of my programs to make use of the Google libraries.  I do like their programming model, which emphasises immutable classes.

Are they faster than the Java Collections API?  Well, they do not seem to offer any perceivable execution performance advantages.  However, the API has been designed with the programmer in mind — this makes these libraries easier to use, and certainly a lot more predictable.  There is no guessing how a method would perform, you can actually code without looking deep into the API.