Several time recently I've seen UDF suggested as the solution to a cross platform format for a drive used on Linux, Mac OS X and Windows XP and above.

I've searched here and not found the same suggestion (most are suggesting ntfs-3g which seems to cost money and isn't preinstalled on a Mac).

So my question is: how is this done right, and has anyone done this? Have you then filled up the drive and deleted some files to make space finding that everything works like a real r/w format even though it seems to have been primarily a write once format?