No slowdown for me.
Laptop computer
CPU Speed: 2.00 GHz
Memory: 3GB RAM (DDR2)
Graphics: "Mobile Intel(R) 4 Series Express Chipset Family" (with 1293MB on-board memory)
Operating System: Windows 7 Home Premium (x32)
There are two other setups I can test, and if and when I do, I'll add them to this post. One of the test subjects is the same computer but in Ubuntu (assuming I can get KS to run in Linux), and the other possible test subject is a pretty old computer (384MB RAM, a bad processor, and a circa-2002 GPU that can't handle Windows 7).