It is hard to say yet which will be the dominant platform, but it is certainly clear that the management tools infrastructure will be a key player here. No-one is going to want to roll out virtual machine technology across the majority of its server farm without there being a solid and capable management tools infrastructure ready and waiting. Microsoft has worked well here with the virtual machine functionality in System Center - indeed, it can even manage virtual machines hosted on the rival ESX and Xenworks platforms too. For many large organisations, the quality of the management tools will be a key decision issue when choosing their virtualisation platform.
In addition, it should be remembered that Microsoft offers special VM installation licenses. If you have a copy of Enterprise Edition, then you can install it both onto raw hardware and onto four virtual machines. If you have Datacenter Edition, you can install an unlimited number of virtual machines. This is independent and totally decoupled from the base OS choice, so an Enterprise Server license allows for four VMs on VMWare ESX, for example.
In the area of remote application support, Microsoft has done much work by starting to bring together many technologies under the Terminal Services banner. The basic TS client/server engine has been improved and now supports a Gateway capability for enhanced security. This requires the latest version of the RDP protocol client. One wrinkle is that the latest RDP client for Mac from Microsoft, currently in beta, does not support these new capabilities. So caution is required if you want to run a mixed client platform with Terminal Services support.
RemoteApp is much stronger, and the capabilities to mix and match locally delivered applications with remotely running apps is much better than ever before. The Softricity capabilities are not to be overlooked - indeed, for many organisations this represents a major step change in the way that applications can be deployed and managed. However, caution is required because much of this technology is separately licensed at extra cost.
Much work has been done to support the design and implementation of larger wide area networks in the Server 2008 platform. For example, it is now possible to set up a branch office role, whereby the domain controller held on site is read-only. This gives you the benefit of local login but with the assurance that all active directory changes have to be pushed up the line and then propagated back outwards to the edges. For some organisational designs, especially those which have a large number of regional or branch offices in a star design and topology wrapped around a datacenter core, this will have significant impact in the line utitilisation and network design.