when im converting avi's to dvd mpeg2..my cpu goes to 100%..thought i can use the gpu to do some transcoding
Yeah... a lot of this would depend on your setup...
The OpenCL benchmarks that have been released so far are pretty... disingenuous because they only test one kind of operation and it happens to be an operation that GPU's are extremely good at.
Transcoding is usually something that a GPU can be very good at, depending on the format being transcoded to. In essence anything that deals with pixels is going to work pretty well because GPU's are built for handling large numbers of pixels all at the same time (or for that matter, OpenCL is going to be good at dealing with large amounts of data that can all be processed in parallel.) However, if you have something like a new Mac Pro, the GPU alone probably isn't going to compete as well with the CPU's, but it would still make a nice co-processor.
OpenCL is not going to be as useful in programs like Mail, Safari, Address Book, iCal, etc. These all deal with small amount of data, and it's going to take longer to move that data into OpenCL than it would to just do it on CPU alone.
But yeah, maybe someday for Toast transcoding. At least OpenCL is a cross platform standard, that should help adoption.