I work at Shopping.com and we've just rebuilt 3 major public-facing applications using Tapestry. The old versions were Perl/Mason.
With a core team of 3 strong Java developers, 1 CSS/HTML person, and 1 Oracle DB developer, we rebuilt what was estimated to take 4 man years in 4 months with some time to spare. I seriously don't think we would have been able to pull this off in Struts/JSP which was the runner up choice for us. In fact I think it could have been a disaster, taking much longer. The application is fairly complex and includes very rich I18N functionality such as rendering of strings in various language (from resource bundles & from the database), rendering currencies, collation by language, etc... Anyway, it was a huge application, and it has been a huge success. I am happy about it and needless to say, so is the business.
I've used many frameworks and have been doing web development for years in the Bay Area. Previously, I've managed and implemented large projects in ASP.NET with back-end Java components. I actually like the class-backing-a-page design of .NET which is similar to Tapestry, except for the fact that ASPX has the same pitfalls as JSP, and it's not Java.