I have to admit that OpenCL is more stylish, and in many ways easier for others to understand. However it takes time to become familiar with it, so why not use GLSL?
While it's true, using some tricks or hacks you can do alot of things in the shader, that where never to be done on it.If you need an example, take a look at my (still work in progress) website. Or look around the web for more examples of creative shader usage. (The examples you can find on the web are probably less hackish...)To support shadowomf, i claim that you can do the same things in a shader as in OpenCL. You only need to think innovative, in other words use framebuffers, textures and transform feedbacks, then you can do pretty much whatever you want.