I am very happy about the performance of Kubuntu 11.04! My old laptop only has Duo T7500 and 4GB Ram. T7500 has only 2 cores(2Ghz) and 4MB Cache. In such configurations, I found my old laptop is not much worse than my new laptop(Win7) which has i7 2630 QM and 8GB RAM. 2630GQM has 4 cores (2Ghz) and 6MB Cache. I think at least 2 times powerful than my old laptop, that has double number of CPU cores and RAM. Kubuntu is done a great job!