In the past it could be said that JDeveloper and ADF hadn't any market penetration because all the available online articles and posts just talked about building applications, with no real consideration of best practices or production deployment considerations.
Over the last year I've noted that this generalisation is no longer true, with a series of excellent articles and posts coming out, such as Simon Haslam's I mentioned in a previous post, and now a new series by John Stegeman.
John Stegeman's ADF Development Essentials series is available from OTN. John's series of articles currently includes practical examples of working with Subversion version control software within JDeveloper, but more importantly how to effectively use it in a team environment and gotchas teams should watch out for. In addition the upcoming parts of the same series will include information on Ant scripting, Unit Testing and Continuous Integration Builds.
The articles are well worth the read for anybody serious about working with ADF applications in a production environment and understand what's involved in serious ADF development. As I've said on the ADF Methodology group before, adopting ADF is just not about building ADF applications, but changing your technical and business environment to improve your software delivery process.