From this presentation, OpenCV 3.0:
- Refined C++ API
- Use cv::Algorithm everywhere
- C API will be marked as deprecated
- Old Python API will be deprecated
- Monstrous modules will be split into micromodules
- Extra modules
- Sufficiently improved CUDA and OpenCL modules
- Hardware Abstraction Layer (HAL)
The latest stable release is OpenCV 2.4.11. OpenCV 3.0 is currently in development and should be released soon.
There should not be so much differences between OpenCV 2.4.11 or OpenCV 3.0.0 if you use the C++ API and if the functions you use are present in both. If you have encountered few bugs, stick with the latest stable release and wait for the release of OpenCV 3.0. Some minor syntax and modules changes may be necessary to adapt your code with OpenCV 3.0 but nothing really big.