Hello. The web based application I am working on currently is a port from a windows application. This application is very data intensive. There are scores of modules and each of these modules have number of forms (data entry screens) and reports whereas the forms have many many fields and likewise the reports.

I have been trying to identify the most suitable architecture for the presentation tier. There are many functions that are not very easily portable, for example printing (this too is very complex). For most of the others, I am planning to us "Ext JS" library which looks like capable of handling about 70% of complexity out of the box while for the remaining I would be custom coding or extending Ext JS.

Having said that (sorry for being so descriptive), I wonder, if this is an Intranet application, why not port the entire application to SilverLight? While I am good at .Net, I'm somewhat alien to SilverLight. Considering I know my target audience and that the software will be used per seat license, would it be better to ride on SilverLight or is it better to stick to conventional web (XHTML, JS, CSS, etc)? Further, I have to support multiple devices in future and considering that SilverLight plug-ins for many devices are yet not out, would it be a risk?