Please read the rooting instructions carefully and read the entire thread over at XDA-Developers. I say this as a positive and a cautionary tale. The devs who put the kernel root cwm package together have made it clear that you MUST disable voodoo before attempting to return your Charge to stock image and do not attempt to restore your Charge (if running voodoo) with CWM Recovery, they are working on that part. Failure to pay attention to those two items (pretty simple) will result in problems you don't want.
Now that said, converting from rfs to ext4 does greatly improve the Charge and I look forward to converting mine soon.