[OT] Jitter, Open Frameworks, Processing, etc … which and when?

Well, this is a kind of very big question. I think programs like jitter and vvvv are very good prototyping/performing tools. The available resources(glsl/hlsl shaders, javascript, c/c# plugins dev, java) can be used to generate great audiovisual material. However, IMHO the bottleneck is: more complex things you want to implement, less debugging tools you have available and documentation can be rather poor. If you get familiar enough it is possible to port all kind of things from processing or other programs.
OFW and Cinder are amazing tools, really. In particular I find cinder very fresh and powerful. However, the learning curve can be slightly slower, starting from the process of learning how to use IDE like Xcode. Also, c++ is a beautiful language but complex to understand in some levels(generic programming, containers, shared pointers, etc). The nice thing is that in both toolkits you have access to many interesting libraries(Bullet, Cairo, OpenCL, OpenGL, ARToolkit, etc). Cinder is made with boost and OFW with Poco; some people prefer the later because is more compact. Also, you have access to the iPhone sdk, although i would suggest to learn a little bit of objective-c and openGLES for that.
I find processing in-between. it is rather easy to learn but you can dive on it deeper and deeper. When used together with eclipse you can do all kind of funky things with it. java also is a very friendly language that can be used as a step towards c++/c. I personally don't like their interface, i find a little bit impractical. Good learning tool.
Maybe it would be worthy to mention quartz composer. Great application that can be extended with the writing of externals(using objectiveC). I mostly prototype my shaders there because the tools are very friendly for that. Also, you can use different core image filters. Can be integrated with VDMX and Resolume. Bottleneck: is there any documentation?

hope it helps!