DHCPv4 is a key protocol in TCP/IP, comparable in importance and widespread deployment to DNS. A very high percentage (90%+?) of nodes running TCP/IP use DHCPv4 for network configuration, including enterprise networks and home users. DHCPv6 is nowhere near as widely supported.
Virtually every platform that supports TCP/IP includes a DHCPv4 client (including mobile platforms). A few platforms already provide DHCPv6 clients, but this is not as widespread. DHCPv6 clients are available on all Windows versions since Vista. Most commercial versions of UNIX (AIX, HP-UX, Solaris) include DHCPv6 support . A free (but mostly unsatisfactory) DHCPv6 client is available for FreeBSD and Linux. Some commercially supported Linux variants have DHCPv6 client support (Fedora 9, Red Hat Enterprise, SUSE Enterprise). Mac OS-X includes support since Lion. Apple iOS has had DHCPv6 support since version 4.3.1. Android currently has no support for DHCPv6. Windows Phone 7.5 has no DHCPv6 support. Information on current support for IPv6 and DHCPv6 is available here. The “ND RDNSS” mentioned there refers to obtaining DNS address and search string information during SLAAC (RFC 6106).
DHCPv4 and DHCPv6 servers are widely available, in Windows Server, FreeBSD, Linux, etc. The Internet Software Consortium (ISC) provides free, open source servers for both DHCPv4 and DHCPv6. Most DNS appliances include full DHCPv4 and DHCPv6 server support. Microsoft provides free DHCPv4 (since the very first Windows NT Server) and DHCPv6 servers (since Windows Server 2008). They are both managed by the same DHCP GUI management tool.