In the past I have primarily built all my web applications using an N-tier architecture, implementing the BLL and DAL layers. Recently, I have started doing some RoR development
We have already use the MVC for the Windows application,Now we need to convert that thing in the Web application we don't have any problem in any thing. We are using the Web service and every Business Logic is in the Web service. So you can use the MVC in the web application. M-Model(Functions and Procedure which communicate with Business logic) V-View(Design) C-Controller(Form Logic) so that is no connection in the DAL,BLL and in MVC. you can define your Business logic and use in it any where in the MVC. That's my point of view MVC is very useful for Re-usability i prefer if your application is big then you must use MVC.