ntfs-3g for mac has the merit to exist. Unfortunately, last time I checked it was *extremely* slow (maybe that's what you get with FS in userspace?), you had to reinstall it on a regular basis because it randomly stopped working... not really usable for lambda users (and unfortunately, lots of mac users are not tech savy).
Then I discovered Paragon NTFS, which is commercial but definitely worth it. Works flawlessly, speed is as good as hfs+ volumes, it's some really nice work. But you have to pay 40$ for it :/