I am going to take a wild guess and say the sluggishness you are encountering is caused by the IO scheduler. It's the main cause of sluggishness on my desktop. In fact it's choking /right now/ as I type this due to a large file copy process in the background. BFQ, the other desktop scheduler for linux, is not included in the default kernel, and in my use has not fared any better.
I could not edit, so I will reply instead. If you work from the terminal I find that prefixing commands with a ``ionice'' priority settings helps keep IO hogs from slowing the desktop.
