ZDNet have reviewed Samba 2.0.2 and the result show Samba beats NT performance-wise for more than 10 concurrent users. In fact the performance for NT degrades extremely fast for higher numbers of clients. The latest version of Samba can act as a PDC and the next version (2.0.5) should be able to act as a BDC as well. It's so difficult to compare two dissimilar operating systems, even when run on the same hardware. But in this case it's clear that Linux is winning hands down in the scalability game.