Samsung Galaxy Note users (as well as other ICS device users) who root and update the OS of their device to leaked builds need to be very careful at the moment. Due to a problem with some Galaxy Note devices as well as other Samsung devices, the leaked builds are bricking some devices.
It turns out that there is a major bug in the leaked ICS kernel that affects the /data partition in the eMMC chip, which apparently gets corrupted during certain operations such as wiping and flashing.
XDA-Developers is a forum whos members find leaked builds of operating systems, tweak them, install them, distribute them and at the same time break things, roll back things and test with newer leaks. However, this bug is now causing a bit of a headache as it is hard bricking some devices.
The bug that causes devices to be bricked is found in the kernel of a version of ICS that was leaked. Some stock recoveries have also seen issues though.
As well as that problem, there's also problems with some CWM.zip files that are distributed around the site. The admins are busy removing bad versions although for now, if you want to root and install an update, check out this thread on the forum for more in-depth details to ensure you don't run in to problems.
These types of problems are why I often warn when mentioning rooting a device and installing an unofficial update. These types of updates are unsupported by manufacturers and hence, if you run in to problems (which is rare I would admit) then you might struggle to get your device up and running again.