If you're looking for a framework to try out on your next Web 2.0 application, Knut Urdalen suggests you give Yii a try.

The Yii Framework is built for speed and the goal is to provide the best possible framework for your next large-scale web 2.0 applications. With it's superior performance, Yii still provides an easy-to-use and highly extensible feature set that is richer than most other frameworks.

If you haven't tried it, he points out the "getting started" tutorial offered on the Yii site as well as some of the performance benchmarks (including those for the next release, 1.0.1).