Performance during Video and Image Editing
Well-known Adobe software for video processing and image editing are optimized for multi-processor systems and Hyper-Threading technology. Therefore, dual-core AMD CPU appeared extremely fast in Photoshop, After Effects and Premiere. It got dramatically faster than not only Athlon 64 FX-55, but also Pentium 4 CPUs, which have always been better in this type of tasks.
Performance during Text Recognition
Pretty popular ABBYY Finereader utility for optical character recognition is optimized for CPUs with Hyper-Threading technology, but works as a single thread only with the dual-core Athlon 64 X2 processors. It looks like there is an evident software bug there: the multi-threading support is detected by the CPU model name.
Unfortunately, there are more examples of such software bugs out there today. We can only hope that there are very few applications like ABBYY Finereader, and this number will one day become 0.