I've been continuing to do work on speeding up Tapestry performance; I think part of the Tapestry message is not just how easy it is to get started, but how the framework grows with you as your application, and your user base, grows.
One aspect of performance is speeding up server side operations, and Tapestry 5.1 has gone a long way down that path. However, there's only so far that can take you, especially since the lion's share of server-side time is spent waiting for database queries.
Another approach is to minimize both the number of requests and the size of the replies. Tapestry 5.1 will GZIP compress replies for dynamic page content and static asset files. That reduces the size of each reply (when the client supports GZIP compression, which all modern browsers do).
The best part is, like many features in Tapestry, there's no configuration to worry about. It just works, it's free, there's no special scripts or tasks to run as part of your build. Better yet, it defaults to off for development mode and defaults on for production mode.