I took a look at the Petshop v3.0
all I can say is , it's not something I would have recomended for customers to see and learn about best practices in real world application.
1. they said they now support oracle , that's great but why copy the code in the Data Layer and not use Object Oriented and make an abstraction layer to the DataBase (I even think there is a document about how to support the DataLayer using only Interfaces ).
2. the oracle helper and the sqlhelper has the same code, point 1 is relevant here too.
3. Factory pattern: they used a so called "Factory" for the Data Access Layer but still produced a class for each dal, I don't call it a factory , I just can't . if they would've done it properly they wouldn't  need to produce a class that does the same code (even the reflection code repeats itself in each class).
4. code reuse - there is non in this application , at least in the Business Layer. a real world application has to maintain the code over time, code reuse helps writing less code , debugging less code and maintaining less code.
5. this application is not scalable, coupling the Business Layer with the Front End one is for small application, when you build E-Commerce site you would like to seperate it.
I know that they are going to do performance tests against a newer version of Java petshop, but why claim they use best practices on the .net version , that's bad PR for .net.  They better do all the code inline and that will surely beat Java.
I'll summit it: I don't like this version it doesn't teach you too much except for defining each layer responsibility, they didn't go all the way as they should have. I don't see a big diffirence between this versoin v2.0 , well ok they cleaned it , did some layering but that's it. I really don't get it .