The Dev CD has many documents and references that make programming the Amiga much easier. However, there is no GUI like MSVC++ for the Amiga. The closest thing you will find is either Storm C++ (version 3 is on the Dev CD for free, version 4 is the latest) and HiSoft C++. Storm C++ 4 is probably the best Amiga compiler package out at the moment. GCC is the best free alternative, but doesn't have a GUI. These two packages are the only truly modern C++ implementations on the Amiga. HiSoft C++ is less expensive and has a great GUI, but the compiler is not without its problems. In addition the Amiga has many great ANSI C compilers including SAS/C and vbcc among others.
I would suggest getting the CD if you intend on getting into serious Amiga specific programming such as graphics and system programming. If you intend to stick to ANSI C/C++ then most of the info on the disk is not very helpful.
The best resource for Amiga programming is on the web naturally, so as others have said, ask away.
