Ultra Hosting provides various levels of virtual servers, dedicated servers and server colocation. They do not provide shared web hosting. They claim to offer high reliability starting with a large staff of technicians, good management processes, continuous improvement, etc.
They offer management services in which their staff takes some of the load of managing the server. This includes monitoring, rebooting as necessary, security hardening, software install, etc. All this depends on the level of service you buy.
They also offer unmanaged dedicated servers, virtual private servers, and server colocation.
They are a green webhosting provider. They achieve this by partnering with CarbonFund.org to offset their carbon footprint. They also describe abiding by the phrase: "Reduce What You Can, Offset What You Can’t.™" They discuss various strategies to reduce power and resource requirements such as consolidating data centers, server virtualization, retiring older servers, etc.