I like the ability to use DDL files to build my own data model, which is very useful for prototyping. It's not exactly intuitive, but it does work well once you get used to it. Also, there are some limitations that make me wonder if this is really a "write your own" kind of thing. For example, you can't use other languages than SQL Server natively, so you have to write your own wrappers around things. So, it's not a full-on open source solution. This would be great if it were! But, we're stuck with what is available. We've been able to solve our problem using DAML, and it has helped us be more efficient in our development.