Most of the uses that you mention involve processing large (ish) amounts of data, and that's one of the drawbacks to GPUs. They're great as long as everything fits into the amount of RAM on the card. Otherwise you're limited by the PCI bus and you're constantly shuttling data back and forth from main memory. It's frustrating when you only have 6GB of RAM on the GPU and 96 or more attached to the CPU. They're just not that good at data processing.