Ben Gidley has done a detailed analysis of Tapestry 5 performance He used some quite reasonable assumptions, including running tests for over an hour to gauge memory use over time. His conclusion is that Tapestry performance is excellent, which is a relief if not a surprise.
What I'm really pleased with is that he's demonstrated that Tapestry will perform well under load; more importantly, if a Tapestry application gets "Slashdotted", it may slow down, but it recovers once the wave of requests dies down.
Ben compared a Tapestry application to a Struts application with similar behavior and found that T5 out-performed Struts pretty handily, despite the fact that T5 doubles the number of requests (due to its automatic redirect-after-post behavior).
Thanks for the great work Ben!