I am in the planning phases for an enterprise level web application that will likely be highly transactional in nature with a SQL Server back end database. Most of my development in the past few years has been implementation of Content Management Systems. However this will be an app that is built from scratch. It seems silly not to use some sort of framework as a starting point to handle the plumbing of the site. Ideally I would like to use some sort of ORM to handle the mapping between the custom objects that I create and the back end database. I have been doing some research on different .NET web application frameworks and I am interested in people's opinions of certain systems like Spring.NET or Express Persistent Objects (XPO) from Dev Express or any others out there that you have had experience with.