ADO.NET :: Which Database Layer To Use?

It's a little bit late for me to be asking this, being already 7 months into development on a large MVC2 web application project for learning languages, but I wanted to get some opinion about what the recommended path for doing database stuff is.Having had no prior experience with commercial databases, I'm pretty confused with all the different options out there.

Because the ASP.NET MVC books use Linq to SQL in the examples, it looked pretty easy, so I just went ahead and used it.My first mistake was that for the models I created abstract interfaces, and then a stand-alone concrete implementation that I could load and save using XML, so I could develop the rest of the application while building up the data model, thinking I could easily provide an alternate implementation of the model classes using Linq to SQL to back it, not using the database design page, just letting the table objects and context do the work. Not being experienced with databases, however, my models were not so easy to reimplement for the database. I'm just about to the point where it is working, albeit there are a few performance problem areas.

So, is Linq to SQL generally the way to go for database stuff? Or is there a more recommended path? I love the simple mapping Linq to Sql provides, but discovered I had to spend a lot of time trying to work around some of its quirks and missing functionality. I found that SQL itself has it's own quirks too, such as problems mixing and matching different languages in strings.

Ideally, I would want something that lets me have a data model that's like an arbitrary heterogenious object tree, using normal collections, and still be able to deal with lots of items with good performance.