What's the good framework for developing a web 2.0 application?

This is a question that I have been asking myself for sometime now. First of all, I wasn't sure whether a web application was such a good idea since I had spent most of last year working with thick clients. So for the moment, Iam setting aside this question, to be able to objectively decide which framework would be the best for data oriented projects. I am saying data oriented because if it were a text editor or had lots of charts, graphs etc, a thick client would win hands down. So the project has to be such that both a thick client as well as a web application can handle. With RIAs the gap between thick and thin clients has definitely narrowed down. This should only aid us in our evaluation.
Let's take a sample project for our evaluation. Since there are a number of web component frameworks available, let's assume we will be using one such component. The Tree component would be a good component to use. The data for the tree itself could be something hierarchical like an organization hierarchy. A requirement of 'Shenandoah corp' could be to get each employee to fill in a questionnaire. So for each employee, a form has to be presented and their inputs taken and then stored in the database. Soem fields in the form might require interfacing with the company's databse in DB2 which might require a web service call to be made. Since the budget for this project is low, the entire development has to be completed in 1 man month. The company also has plans to showcase the application to their customers which would imply that the application be web 2.0. It wuld therefore have to use Ajax and provide the same experience as visiting a site like digg, flickr etc. With the above in mind, let's proceed to narrow down the tool/api/frameork to use to implement this. To begin with, the available frameworks are as follows:

1. Flex 2
2. Wicket
3. Ruby on rails
4. GWT
5. J2EE
6. Seam
7. Struts

Since Ajax is needed, no 5 and no 7 are eliminated right away unless some means of Ajaxifying j2ee and struts is available. The rest are all even contenders which leaves us with nos:

1. Flex2
2. Wicket
3. Ruby on Rails
4. GWT
6 Seam

the eighth ofcourse being the Swing based thick client.

Who won the race and which framework was finally chosen to build the application. Watch this space to know the ending.