A pretty constant request is "does Tapestry scale?" Can you run really, really big applications with thousands of users on Tapestry?
Nothing we can say about the design of Tapestry can substitute for real examples.
http://www.NHL.com is largely implemented using Tapestry. It uses a mixture of traditional, live Tapestry applications with scripts that "scrape" Tapestry apps at intervals to create static web pages. During peak times, nhl.com can get seven million hits per day. We broke an NHL record a few weeks back. 11 million page views (3.6M unique users) in an 18 hour period.
Only a handful of the pages are flattened, though they tend to be the main entry points to the site. Tons of dynamic content is generated off of them.
The stats application pages are completely dynamic. ( http://www.nhl.com/nhlstats/stats ) Every request is handled by the Tapestry application. At the start of the 2003-04 playoffs, we've had over 100,000 (totally Tapestry-generated HTML) page views in our stats app in just over 7 hours.
Cayenne deserves a lot of the credit here as well. Both frameworks have saved us a ton of work.
Another site that receives five to eight million hits per month (that works out to at least 7,000 per hour). Much more of the site is dynamic than NHL.com, though a limited amount of scraping and caching does occur. In addition, a lot of effort was involved in keeping the application stateless (no HttpSession).