I've started to use the IPython Notebook and am enjoying it. Sometimes, I write buggy code that takes massive memory requirements or has an infinite loop. I find the "interrupt kernel" option sluggish or unreliable, and sometimes I have to restart the kernel, losing everything in memory.
I also sometimes write scripts that cause OS X to run out of memory, and I have to do a hard reboot. I'm not 100% sure, but when I've written bugs like this before and ran Python in the terminal, I can usually CTRL+C my scripts.
I am using the Anaconda distribution of IPython notebook with Firefox on Mac OS X.
You can press I
twice to interrupt the kernel.
This only works if you're in Command mode. If not already enabled, press Esc to enable it.