Ugh, 2000 domain controllers suck. Slow intrasite replication, lack of a strict replication feature, no 64-bit DCs, no application partitions, no multi-value attributes, no universal group caching, shitty tools, no GPMC (you could use an XP box for that, oh wait, XP sucks right?), etc, etc.In 99% of the situations, there is no reason a business needs anything more.
Also, IIS5 anyone? Smartcard support? Firewall?
2000 was a great OS, but to ignore the improvements in Server 2003 and XP (I'll take 256-bit AES EFS over 3DES thanks) is really shortsighted. To the point of blindness.