We're experiencing the same issue with only 800-1000 rows, 9 columns per row. After the load, the page continues to be hesitant in responding to clicks or hover actions.
In Mamun's dojo above, the data indeed loads relatively quickly, but you'll notice that any mouse actions after load take considerable time to respond. Try it. After the grid loads, click on the drop down at the bottom.
There is something definitely eating up CPU and not letting it go in the kendo ui grid. We're still using version 1.6.0.
Is there any kind of option we can turn off/on to reduce the number of event listeners being generated?