I would like to add to this thread that recently I have had an opportunity to use an OR Mapper at work, specifically Wilson OR mapper. I definitely see the benefits in terms of rapid development but in addition to the other points I have made here about why I don't think I should use an OR mapper in mojoPortal I would like to add another reason.
OR Mappers and code generation tend to lead to a one to one correspondence between classes and db tables. In the book
Object Thinking, the author makes an argument that I agree with that this approach is data driven development and not true OOP. In tru OOP you want to think about the natural joints in your object hierarchy. While it is true that you often naturally have a correspondence between tables and classes this is not always the way your object hierarchy should be and you end up with what the author describes as an explosion of classes.
I use code generation to stub out standard db crud code but I don't do it in a way where you can re-gen if you add a column because I don't always have a class for every table but I still get a jump start on development with this approach.
Using code generation with the re-gen approach or using OR mappers forces you into this one to one correspondence and I don't favor this approach for an art project like mojoPortal, though I could see the benefit of doing it in many projects where reduction in time to development may be a higher priority.