TheServerSide has just published an interview with Kito Mann, author of JavaServer Faces in Action. Of course, I'm not a fan of JSF -- my limited research shows that it does too little and requires too much code, but I suggest you read the article yourself. It's gratifying to me to see how, over the last two years, Tapestry has migrated to the front of any discussion concerning web application development.
I think one of the key words that comes up in the interview with respect to Tapestry is mature (and stable). Tapestry has grown into its current state in fits and starts ... a significant core has not changed radically in the last four years (Tapestry started in January 2000), but quite a bit of Tapestry today has come about in response to actual user's needs and requests. In fact, starting with a small, smart, involved user base meant that Tapestry could make some significant (and non-backward's compatible) changes early in its life.