There is a recent driver out for Read/Write support of NTFS drives under Mac OS X.
There is now an NTFS-3G item in the system preferences. I would recommending unchecking the "File system Caching enabling". This with disk caching the mutliple read writes to the same data can be much faster but can corrupt the disk if the buffer is not flushed before removal. Ejecting or unmounting the disc is the way you tell the computer you want to flush the buffers and remove the disk. BUT I occasionally forget to do this for external discs and I dont want to lose all my data. On the plus side I do not work (edit data) on external discs just transfer/Archive data or play/read files so I do not see any performance loss.
The new driver also has a force button for when windows did not shut it disc down correctly. So you can force OS X to load the disc any way, this was a real pain in my old version of the driver.
Release Notes Updates can be found here: