The DocProject 1.10.0 Release Candidate is now available for download on CodePlex.
It contains lots of bug fixes and some new features that I hope you'll like. You can read my preview post for information on a few of the more important features that have been added, and a comprehensive list of all of DocProject's features is available here.
Be aware that I'm still in the process of updating the wikis on CodePlex, which can take a while.
If you feel like you want to leave a comment here, or tell me about your experiences with the new version of DocProject, good or bad, please go right ahead :)
Oh, and one more thing, Conceptual Content!!!
Now you can use DocProject to build a .CHM and .HxS for conceptual documentation, without the need for auto-generated reference topics.
In other words, DocProject automates the Microsoft HTML Help Workshop and Help 2.x compiler to build conceptual documentation right inside of Visual Studio using Sandcastle's conceptual build process and MAML, so the output looks identical to a presentation style such as Sandcastle's Visual Studio 2005. (Note that I haven't even attempted to build conceptual documentation with the other presentation styles since they were not tested by Microsoft.)
Getting Started With Conceptual Content
Create a new DocProject or DocSite and you can immediately start writing your conceptual documentation in Visual Studio's XML editor, with full IntelliSense for MAML schemas. (Though it seems that you may need to open your project's Help\Schemas\developer.xsd file in the designer first before you'll get IntelliSense.)
To get started, press the Topic Explorer button on the Sandcastle tool bar 
and then add a conceptual topic by clicking
on the Topic Explorer's tool bar. DocProject will ask you which template you want to use. For general documentation use the template named simply, Conceptual. If you don't need auto-generated reference documentation, then you can build the project now and it will produce conceptual-only documentation.
Mixed Documentation
But even better, if you do have APIs that you want documented, DocProject will build all of your topics together as a single conceptual/reference project without any additional requirements. Simply add references to your source projects and build.
If a DocProject or DocSite has one or more sources for documentation (external or project references) then an auto-generated root topic for reference documentation will appear in Topic Explorer. You can add new conceptual topics to the TOC relative to the root reference topic and even drag & drop conceptual topics and the root reference topic to produce the TOC that you want. Add as many conceptual topics and sources as you'd like, then build. That's it!
Enjoy :D