I'm obviously a fan of the Sincpac-C3D, as its creator...
But one feature is that it lets you create Annotatve MText/MLeaders/Dimensions that match your DViewTWist.. Makes life SO MUCH simpler in most cases. But this involves third-party support, as mentioned earlier in this post... This is one of the "minor" additions of our software, which can still save you so much time that it pays for itself. There are dozens of other additions that provide a far greater benefit. We constantly get feedback from users that they wish Autodesk would include our functionality in the default release of C3D, because it is so much easier to use C3D with the Sincpac-C3D. than to use C3D by itself.